Retroreflective article comprising embedded reflective layers

ABSTRACT

A retroreflective article including a binder layer and a plurality of retroreflective elements. Each retroreflective element includes a transparent microsphere partially embedded in the binder layer. At least some of the retroreflective elements include a reflective layer that is embedded between the transparent microsphere and the binder layer. At least some of the embedded reflective layers are localized reflective layers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US2018/057561, filed Oct. 25, 2018, which claims the benefit ofprovisional Application No. 62/739,489, filed Oct. 1, 2018, andprovisional Application No. 62/578,343, filed Oct. 27, 2017, thedisclosure of which is incorporated by reference in its/their entiretyherein.

BACKGROUND

Retroreflective materials have been developed for a variety ofapplications. Such materials are often used e.g. as high visibility trimmaterials in clothing to increase the visibility of the wearer. Forexample, such materials are often added to garments that are worn byfirefighters, rescue personnel, road workers, and the like.

SUMMARY

In broad summary, herein is disclosed a retroreflective articlecomprising a binder layer and a plurality of retroreflective elements.Each retroreflective element comprises a transparent microspherepartially embedded in the binder layer. At least some of theretroreflective elements comprise a reflective layer that is embeddedbetween the transparent microsphere and the binder layer. At least someof the embedded reflective layers are localized reflective layers. Theseand other aspects will be apparent from the detailed description below.In no event, however, should this broad summary be construed to limitthe claimable subject matter, whether such subject matter is presentedin claims in the application as initially filed or in claims that areamended or otherwise presented in prosecution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side schematic cross sectional view of an exemplaryretroreflective article.

FIG. 2 is an isolated magnified perspective view of a single transparentmicrosphere and an exemplary embedded, localized reflective layer.

FIG. 3 is an isolated magnified side schematic cross sectional view of asingle transparent microsphere and an exemplary embedded, localizedreflective layer.

FIG. 4 is an isolated magnified top plan view of a single transparentmicrosphere and an exemplary embedded, localized reflective layer.

FIG. 5 is a side schematic cross sectional view of another exemplaryretroreflective article.

FIG. 6 is a side schematic cross sectional view of another exemplaryretroreflective article.

FIG. 7 is a side schematic cross sectional view of an exemplary transferarticle comprising an exemplary retroreflective article, with thetransfer article shown coupled to a substrate.

FIG. 8 is a side schematic cross sectional view of an exemplaryretroreflective intermediate article, comprising a carrier layer bearingtransparent microspheres with exemplary isolated reflective layersdisposed thereon.

FIG. 9a is a scanning electron microscope secondary-electron 200×photograph of an exemplary Working Example article comprising a carrierlayer bearing transparent microspheres with embedded, localizedreflective layers disposed thereon.

FIG. 9b is a scanning electron microscope backscattered-electron 200×photograph of the same portion of a Working Example article as FIG. 9 a.

FIG. 10a is a scanning electron microscope secondary-electron 500×photograph of a portion of an exemplary Working Example articlecomprising a carrier layer bearing transparent microspheres withembedded, localized reflective layers disposed thereon.

FIG. 10b is a scanning electron microscope backscattered-electron 500×photograph of the same portion of a Working Example article as FIG. 10a.

FIG. 11a is a scanning electron microscope secondary-electron 1000×photograph of a portion of an exemplary Working Example articlecomprising a carrier layer bearing transparent microspheres withembedded, localized reflective layers disposed thereon.

FIG. 11b is a scanning electron microscope backscattered-electron 1000×photograph of the same portion of a Working Example article as FIG. 11a.

FIG. 12 is an optical microscope 300× photograph of a portion of anexemplary Working Example article comprising a carrier layer bearingtransparent microspheres with embedded reflective layers disposedthereon.

FIG. 13 is a front-lit optical microscope photograph of a portion of anexemplary Working Example retroreflective article.

Like reference numbers in the various figures indicate like elements.Some elements may be present in identical or equivalent multiples; insuch cases only one or more representative elements may be designated bya reference number but it will be understood that such reference numbersapply to all such identical elements. Unless otherwise indicated, allnon-photographic figures and drawings in this document are not to scaleand are chosen for the purpose of illustrating different embodiments ofthe invention. In particular the dimensions of the various componentsare depicted in illustrative terms only, and no relationship between thedimensions, relative curvatures, etc. of the various components shouldbe inferred from the drawings, unless so indicated.

As used herein, terms such as “front”, “forward”, and the like, refer tothe side from which a retroreflective article is to be viewed. Termssuch as “rear”, “rearward”, and the like, refer to an opposing side,e.g. a side that is to be coupled to a garment. The term “lateral”refers to any direction that is perpendicular to the front-reardirection of the article, and includes directions along both the lengthand the breadth of the article. The front-rear direction (f-r), andexemplary lateral directions (1) of an exemplary article are indicatedin FIG. 1.

Terms such as disposed, on, upon, atop, between, behind, adjacent,contact, proximate, and the like, do not require that a first entity(e.g. a layer) must necessarily be in direct contact with a secondentity (e.g. a second layer) that the first entity is e.g. disposed on,behind, adjacent, or in contact with. Rather, such terminology is usedfor convenience of description and allows for the presence of anadditional entity (e.g. a layer such as a bonding layer) or entitiestherebetween, as will be clear from the discussions herein.

As used herein as a modifier to a property or attribute, the term“generally”, unless otherwise specifically defined, means that theproperty or attribute would be readily recognizable by a person ofordinary skill but without requiring a high degree of approximation(e.g., within +/−20% for quantifiable properties). For angularorientations, the term “generally” means within clockwise orcounterclockwise 10 degrees. The term “substantially”, unless otherwisespecifically defined, means to a high degree of approximation (e.g.,within +/−10% for quantifiable properties). For angular orientations,the term “substantially” means within clockwise or counterclockwise 5degrees. The term “essentially” means to a very high degree ofapproximation (e.g., within plus or minus 2% for quantifiableproperties; within plus or minus 2 degrees for angular orientations); itwill be understood that the phrase “at least essentially” subsumes thespecific case of an “exact” match. However, even an “exact” match, orany other characterization using terms such as e.g. same, equal,identical, uniform, constant, and the like, will be understood to bewithin the usual tolerances or measuring error applicable to theparticular circumstance rather than requiring absolute precision or aperfect match. The term “configured to” and like terms is at least asrestrictive as the term “adapted to”, and requires actual designintention to perform the specified function rather than mere physicalcapability of performing such a function. All references herein tonumerical parameters (dimensions, ratios, and so on) are understood tobe calculable (unless otherwise noted) by the use of average valuesderived from a number of measurements of the parameter. All averagesreferred to herein are number-average unless otherwise specified.

DETAILED DESCRIPTION

FIG. 1 illustrates a retroreflective article 1 in exemplary embodiment.As shown in FIG. 1, article 1 comprises a binder layer 10 that comprisesa plurality of retroreflective elements 20 spaced over the length andbreadth of a front side of binder layer 10. Each retroreflective elementcomprises a transparent microsphere 21 that is partially embedded inbinder layer 10 so that the microspheres 21 are partially exposed anddefine a front (viewing) side 2 of the article. The transparentmicrospheres thus each have an embedded area 25 that is seated in areceiving cavity 11 of binder layer 10, and an exposed area 24 that isexposed (protrudes) forwardly of major front surface 14 of binder layer10. In some embodiments, the exposed areas 24 of microspheres 21 ofarticle 1 are exposed to an ambient atmosphere (e.g., air) in the finalarticle as-used, rather than being e.g. covered with any kind of coverlayer or the like. Such an article will be termed an exposed-lensretroreflective article. In various embodiments, a microsphere may bepartially embedded in the binder layer so that on average, from 15, 20or 30 percent of the diameter of the microsphere, to about 80, 70, 60 or50 percent of the diameter of the microsphere, is embedded within binderlayer 10. In many embodiments, a microsphere may be partially embeddedin the binder layer so that, on average, from 50 percent to 80 percentof the diameter of the microsphere is embedded within binder layer 10.

A retroreflective element 20 will comprise a reflective layer 30disposed between the transparent microsphere 21 of the retroreflectiveelement and the binder layer 10. The microspheres 21 and the reflectivelayers 30 collectively return a substantial quantity of incident lighttowards a source of light that impinges on front side 2 of article 1.That is, light that strikes the retroreflective article's front side 2passes into and through a microsphere 21 and is reflected by thereflective layer 30 to again reenter the microsphere 21 such that thelight is steered to return toward the light source.

Embedded Reflective Layers

As illustrated in exemplary embodiment in FIG. 1, at least some of thereflective layers 30 of retroreflective elements 20 of retroreflectivearticle 1 will be embedded reflective layers. In various embodiments, atleast generally, substantially, or essentially all of the reflectivelayers 30 of retroreflective elements 20 will be embedded reflectivelayers (noting that according to the terminology used herein, atransparent microsphere that lacks a reflective layer will not beconsidered to be a retroreflective element).

An embedded reflective layer 30 is a reflective layer that is disposedadjacent to a portion of an embedded area 25 of a transparentmicrosphere 21 as shown in exemplary embodiment in FIG. 1. An embeddedreflective layer will at least generally conform to a portion (oftenincluding a rearmost portion) of the embedded area 25 of a transparentmicrosphere 21. By definition an embedded reflective layer will becompletely surrounded (e.g. sandwiched) by the combination of at leastthe binder layer 10 and the transparent microsphere 21 (noting that insome embodiments some other layer or layers, e.g. an intervening layersuch as a bonding layer and/or a color layer, may also be present inarticle 1, as discussed later herein, and may contribute to thesurrounding of the reflective layer). In other words, the minor edges 31of the reflective layer (as depicted in exemplary embodiment in FIG. 1)will be “buried” between the transparent microsphere 21 and the binderlayer 10 (and possibly other layers) rather than being exposed. That is,the locations 26 that mark the boundary between an exposed area 24 of amicrosphere and an embedded area 25 of a microsphere, will be abutted byan edge 16 of binder layer 10 (or an edge of layer disposed thereon)rather than by the minor edge 31 of reflective layer 30.

For a transparent microsphere 21 that comprises an embedded reflectivelayer 30, no part of embedded reflective layer 30 will be exposed so asto extend onto (i.e., cover) any portion of exposed area 24 ofmicrosphere 21. Microspheres with embedded reflective layers 30 are thusdistinguished from arrangements made by “randomized bead” processes inwhich microspheres are hemispherically coated with reflective layers andare then disposed randomly on a substrate so that numerous microspheresexhibit at least partially exposed reflective layers. Furthermore,retroreflective elements comprising embedded reflective layers 30 asdisclosed herein will be distinguished from arrangements in whichmicrospheres that have been coated with reflective layers over theentire surfaces of the microspheres are disposed on a substrate afterwhich reflective layers are removed from exposed areas of themicrospheres e.g. by etching. Such arrangements will not result in thereflective areas exhibiting “buried” edges and thus will not produceembedded reflective layers as defined herein.

It will be appreciated that in actual industrial production ofretroreflective articles of the general type disclosed herein,small-scale statistical fluctuations may inevitably be present that mayresult in the formation of a very small number of e.g. minor portions ofa reflective layer that exhibit a minor edge or area that is exposedrather than being buried. Such occasional occurrences are to be expectedin any real-life production process; however, embedded reflective layersas disclosed herein are distinguished from circumstances in whichreflective layers are purposefully arranged in a manner in which theywill exhibit a large number of exposed minor edges or areas.

Localized/Bridging Reflective Layers

In some embodiments an embedded reflective layer 30 will be a localizedreflective layer. By definition, a localized reflective layer is anembedded reflective layer that does not comprise any portion thatextends away from an embedded area 25 of a microsphere 21 along anylateral dimension of article 1 to any significant extent. In particular,a localized reflective layer will not extend laterally to bridge lateralgaps between neighboring transparent microspheres 21. In someembodiments, at least generally, substantially, or essentially all(according to the previously-provided definitions) of the embeddedreflective layers 30 will be localized reflective layers. However, insome particular embodiments (e.g. involving laminated reflective layersas discussed later herein) a reflective layer may bridge a lateral gapbetween neighboring transparent microspheres. In such instances, areflective layer may be sized and positioned so that a portion of thereflective layer is positioned at least generally rearwardly of atransparent microsphere, and another portion of that same reflectivelayer is positioned at least generally rearwardly of another,neighboring microsphere. A single reflective layer may thus operate inconjunction with two (or more) transparent microspheres and will betermed a “bridging” reflective layer. Bridging reflective layers are notlocalized reflective layers as defined herein, however, the perimeteredges of bridging reflective layers are buried between the transparentmicrospheres and the binder material; bridging reflective layers arethus “embedded” reflective layers. An exemplary bridging reflectivelayer (which is dark-colored in appearance in this optical photograph)is identified by reference number 36 in the photograph of a WorkingExample sample present in FIG. 12; this bridging reflective layerappears to bridge three transparent microspheres.

The occurrence of bridging reflective layers seems to be statisticallydriven and is affected e.g. by lamination conditions (as discussed indetail in U.S. Provisional Patent Application 62/739,506; entitled“RETROREFLECTIVE ARTICLE COMPRISING LOCALLY-LAMINATED REFLECTIVELAYERS”, filed evendate herewith and incorporated by reference in itsentirety herein). In some embodiment any such bridging reflectivelayers, if present, may represent a relatively small fraction of thetotal number of embedded reflective layers. Thus in some embodimentsbridging reflective layers may be present at a level of less than 20,10, 5, 2 or 1% of the total population of embedded reflective layers.However, in some particular embodiments, bridging reflective layers mayrepresent as much as 20, 30, 40 or even 50% or more of the totalpopulation of embedded reflective layers.

FIG. 2 is a magnified isolated perspective view of a transparentmicrosphere 21 and an exemplary localized, embedded reflective layer 30,with a binder layer 10 omitted for ease of visualizing reflective layer30. FIG. 3 is a magnified isolated side schematic cross sectional viewof a transparent microsphere and an embedded reflective layer 30. Asshown in these Figures, a reflective layer 30 will comprise a majorforward surface 32 that often exhibits a generally arcuate shape, e.g.in which at least a portion of forward surface 32 at least generallyconforms to a portion of a major rearward surface 23 of microsphere 21.In some embodiments, major forward surface 32 of reflective layer 30 maybe in direct contact with major rearward surface 23 of microsphere 21;however, in some embodiments major forward surface 32 of reflectivelayer 30 may be in contact with a layer that is itself disposed on majorrearward surface 23 of microsphere 21, as discussed in further detaillater herein. A layer that is disposed in this manner may be, e.g., atransparent layer that serves e.g. as a protective layer, as a tie layeror adhesion-promoting layer; or, such a layer may be a color layer asdiscussed in detail later herein. A major rearward surface 33 ofreflective layer 30 (e.g. a surface that is in contact withforward-facing surface 12 of binder layer 10 as shown in FIG. 1, or asurface of a layer present thereon) may be, but does not necessarilyhave to be, at least generally congruent with (e.g. locally parallel to)the major forward surface 32 of reflective layer 30. This may depende.g. on the particular manner in which the reflective layer is disposedon the transparent microspheres, as discussed later herein.

Percent Area Coverage of Reflective Layers

As evident from FIGS. 2 and 3, an embedded reflective layer 30 will bedisposed so that it occupies (covers) a portion 28, but not theentirety, of embedded area 25 of microsphere 21. The remainder ofembedded area 25 will be area 27 that is not occupied by reflectivelayer 30. Such arrangements can be characterized in terms of thepercentage of embedded area 25 that is covered by reflective layer 30(regardless of whether layer 30 is in direct contact with area 25 or isseparated therefrom by e.g. a tie layer or the like). In variousembodiments, a reflective layer, if present on a microsphere, may occupya covered portion 28 that is at least 5, 10, 20, 30, 40, 50, 60, or 70percent of embedded area 25 of the microsphere. In further embodiments,a reflective layer, if present, may occupy a covered portion 28 that isat most 95, 85, 75, 60, 55, 45, 35, 25, or 15 percent of embedded area25. Such calculations will be based on the actual percentage ofmulti-dimensionally-curved embedded area 25 that is covered byreflective layer 30, rather than using e.g. plane-projected areas. Byway of a specific example, the exemplary reflective layer 30 of FIG. 3occupies a portion 28 that is estimated to be approximately 20-25% ofembedded area 25 of microsphere 21.

In some embodiments a reflective layer 30 may be characterized in termsof the percentage of the total surface area of the microsphere (i.e.,embedded area 25 plus exposed area 24) that is occupied (covered) by thereflective layer. In various embodiments, a reflective layer, if presenton a microsphere, may occupy a covered area that is at least 5, 10, 15,20, 25, 30 or 35 percent of the total surface area of the microsphere.In further embodiments, a reflective layer, if present, may occupy acovered area that is less than 50, 45, 40, 35, 30, 25, 20, 15, or 10percent of the total surface area of the microsphere. By way of aspecific example, the exemplary reflective layer 30 of FIG. 3 isestimated to occupy an area 28 that is approximately 10-12% of the totalsurface area of microsphere 21.

In some embodiments, an embedded reflective layer 30 may becharacterized in terms of an angular arc that the reflective layeroccupies. For purposes of measurement, such an angular arc a may betaken along a cross-sectional slice of the transparent microsphere (e.g.resulting in a cross-sectional view such as in FIG. 3) and may bemeasured from a vertex (v) at the geometric center of transparentmicrosphere 21, as shown in FIG. 3. In various embodiments, an embeddedreflective layer 30 may be disposed so that it occupies an angular arc acomprising less than 180, 140, 100, 80, 60, 40 or 30 degrees. In furtherembodiments, a reflective layer may occupy an angular arc a of at leastabout 5, 10, 15, 25, 35, 45, 55, 75, 95, or 135 degrees. (By way ofspecific examples, the exemplary reflective layers 30 of FIG. 1 areestimated to occupy an angular arc a in the range of approximately150-160 degrees, whereas the exemplary reflective layer 30 of FIG. 3 isestimated to occupy an angular arc a in the range of approximately 80-85degrees.) As will be made clear by the detailed discussions later hereinregarding methods of making embedded reflective layers, in manyembodiments an embedded reflective layer 30 may not necessarily besymmetrical (e.g., circular and/or centered on the front-rear centerlineof the transparent microsphere) when viewed along the front-rear axis ofthe transparent microsphere. Rather, in some cases a reflective layer 30may be non-circular, e.g. oval, irregular, lop-sided, splotchy, etc., inthe general manner shown in the generic representation of FIG. 4.Accordingly, if such a reflective layer is to be characterized by anangular arc in the manner described above, an average value of theangular arc will be reported. Such an average value can be obtained, forexample, by measuring the angular arc at several (e.g. four) locationsspaced around the microsphere (with the microsphere viewed along itsfront-rear axis) as indicated in FIG. 4 and taking the average of thesemeasurements. (Such methods may also be used to obtain theabove-described area percentages.)

For a reflective layer that is symmetrically positioned on a microspheree.g. as in FIGS. 1-3, the midpoint of any or all such angular arcs mayat least substantially coincide with the front-rear axis (centerline) ofthe microsphere. That is, for a reflective layer that is bothsymmetrically positioned and is symmetrical shaped, the geometric centerof the reflective layer may coincide with the front-rear centerline ofthe microsphere. However, in some embodiments a reflective layer may beat least slightly offset relative to the front-rear centerline of themicrosphere, so that at least some such midpoints may be located e.g.10, 20, 30, 45, 60, 75, or 85 degrees away from the front-rearcenterline of the microsphere.

In additional to any individual reflective layer possibly exhibiting anirregular shape as in FIG. 4, the reflective layers of differentmicrospheres may differ from each other in shape and/or size. Forexample, in some embodiments reflective layers may conveniently bedisposed on microspheres by being transferred to protruding portionsthereof, while the microspheres are partially (and temporarily) embeddedin a carrier. Since different microspheres may vary slightly indiameter, and/or there may be variations in the depth to which differentmicrospheres are embedded in the carrier, different microspheres mayprotrude different distances outward from the carrier. In some casesmicrospheres that protrude further outward from the carrier may receivea greater amount of reflective layer transferred thereto, in comparisonto microspheres that are more deeply embedded in the carrier. This beingthe case, it will be understood that the reflective layers of variousmicrospheres may differ from each other in terms of the angular arcoccupied by the reflective layer and/or in terms of the percentage ofthe embedded area of microsphere (or the percentage of the total area ofthe microsphere) occupied by the reflective layer.

Such variations notwithstanding, it will be understood thatretroreflective elements comprising embedded reflective layers asdisclosed herein are distinguished from arrangements in whichtransparent microspheres that are hemispherically covered withreflective layers are disposed randomly (e.g. by so-called“randomized-bead” processes) onto binder layers. That is, embeddedreflective layers as disclosed herein will tend to be clustered on ornear the rearmost portion of the microspheres; or, if the reflectivelayers are offset from this rearmost portion, they will tend to beoffset in the same direction. In contrast, randomized-bead approacheswill result in reflective layers that are distributed widely throughoutall possible angular orientations on the surfaces of the microspheres.

An embedded reflective layer may exhibit any suitable thickness (e.g.average thickness, measured at several locations over the extent of thereflective layer). It will be appreciated that different methods ofmaking a reflective layer may give rise to reflective layers ofdiffering thickness. In various embodiments, an embedded reflectivelayer may exhibit an average thickness (e.g. measured at severallocations over the extent of the reflective layer) of from at least0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 4, or 8 microns, to at most 40, 20, 10,7, 5, 4, 3, 2 or 1 microns. In various other embodiments, an embeddedreflective layer may comprise an average thickness of at least 10, 20,40 or 80 nanometers; in further embodiments such a reflective layer maycomprise an average thickness of at most 10, 5, 2 or 1 microns, or of atmost 400, 200 or 100 nanometers. If the reflective layer (or set ofsublayers, e.g. of a dielectric stack that collectively provides areflective layer) is a layer of a multilayer stack (e.g. a transferstack as described later herein), these thicknesses apply only to thereflective layer itself.

The arrangements disclosed herein provide a transparent microsphere witha reflective layer 30 that occupies a portion 28 of embedded area 25that is smaller, sometimes far smaller, than the total embedded area 25of the transparent microsphere 21. In at least some embodiments, thiscan provide significant advantages. For example, this can provide thatacceptable retroreflective performance is achieved (e.g. at least withlight that impinges on the microspheres generally along the front-rearaxis of the article), while also providing that the presence of thereflective layers does not significantly detract from the appearance ofthe article in ambient light. That is, in ambient light the article mayexhibit an appearance that is largely imparted by the composition of thebinder, in particular by any colorants or patterns that may be presentin the binder, rather than being dominated by the presence of reflectivelayers.

In further detail, for a retroreflective article in which the entiretyof the embedded areas of all of the microspheres of the article arecovered with reflective layers, the reflective layers can dominate theappearance of the article in ambient light (e.g. so that the articleexhibits a grey or washed-out appearance). In contrast, the presentarrangements can provide that the “native” color of the article, e.g. asimparted by one or more colorants disposed in the binder layer, can beperceived in ambient light. In other words, enhanced color fidelity orvividness in ambient light can be provided.

It will thus be appreciated that the arrangements disclosed herein allowdesigners of retroreflective articles to operate in a design space inwhich the retroreflective performance, and the color/appearance inambient light, of the article can both be manipulated. While there maybe some tradeoff (e.g. the retroreflectivity may rise as the colorfidelity falls, and vice versa) the design space is such that acceptablevalues of both parameters can be obtained, and can be tailored forparticular applications.

Nonuniform Reflective Layers

The present arrangements tolerate, and even make use of, significantvariability in the reflective layers. That is, it will be appreciatedfrom the discussions herein that at least some methods by which embeddedreflective layers are formed can result in significant variability inthe percent area coverage exhibited by the reflective layers (i.e., inthe size of reflective-layer-covered area 28 in relation to embeddedarea 25) over the population of microspheres. This is evidenced by thevariability in the sizes of areas 28 that are covered by reflectivelayers 30, in the scanning electron micrographs (at variousmagnifications) of various Working Example samples that are presented inFIGS. 9a /9 b, 10 a/10 b, and 11 a/11 b. The “a” Figures are obtainedvia secondary electron imaging, which provides more visual detail. The“b” Figures are the same images but obtained via electronbackscattering, in which high atomic number elements stands out as beingvery light (white) colored. (In the particular Working Example samplespresented in these Figures the reflective layer was metallic silverwhich appeared very white in contrast to the darker colors of the glassmicrospheres and the various organic polymer layers in the “b” figures.)

All of these Figures (as well as FIG. 12) are of carrier-bornemicrospheres 21 with an intervening layer 50 (described later herein)and a reflective layer 30 disposed thereon but without a binder layer 10having yet been formed thereon. However, these Figures are considered tobe representative of how the microspheres and reflective layers would bearranged, after a binder layer had been formed thereon. The occasionaldark-colored cavities visible in these Figures result from through-holesin the intervening layer 50 where the layer precursor did not fully wetinto gaps between the microspheres 21, thus the surface of the carrierlayer 110 is visible (and is dark-colored) through the resulting holesin the intervening layer.

As noted above, FIGS. 9a /9 b, 10 a/10 b, and 11 a/11 b (as well as FIG.12) reveal considerable variation in the area coverage exhibited by thedifferent reflective layers. The particular Working Example samplesshown in these Figures were all obtained by physical-transfer(lamination) methods; however, other methods (e.g. printing, anddeposition/etching) also imparted considerable variation in the areacoverage exhibited by the reflective layers. Still further, as isevident from the higher-magnification micrographs of FIGS. 10a /10 b and11 a/11 b, in many instances transferred reflective layers exhibitnumerous interruptions (e.g. cracks and gaps) within the nominal overallarea covered by the reflective layer. The previously-discussed percentarea coverage may be calculated in disregard of such gaps if they arerelatively insignificant (e.g., if they will not change the calculatedarea coverage by more than 10%). However, if such gaps wouldsignificantly affect the calculated area coverage, they should be takeninto account. The previously-discussed angular arc, however, may becalculated using the nominal outer perimeter of the reflective layer,disregarding any such gaps.

It will thus be appreciated that for a population of retroreflectiveelements, the percent area coverages (and resulting overall sizes)exhibited by the different reflective layers, and the amount and/or sizeof gaps within the different reflective layers, may vary considerably.(Based on the above discussions it will be appreciated that thenon-photographic Figures of the present application are idealizedrepresentations in which, for ease of presentation, the above-discussedvariations are not depicted.) Surprisingly, acceptable or even excellentretroreflective performance can be obtained in spite of suchnonuniformity of the reflective layers. In various embodiments, thepercent area coverage of embedded areas of transparent microspheres byreflective layers, when evaluated over a statistically appropriatesample of microspheres of the total microsphere population, may exhibita coefficient of variation (obtained by standard statistical techniques,and expressed as a decimal proportion) that is greater than zero. By wayof a specific example, a set of microspheres whose reflective layersexhibited a mean percent area coverage of 44 percent and a standarddeviation of 26 percent (in the same units as the mean), would exhibit acoefficient of variation of 0.59.

Reflective layers with percent area coverages (of the embedded areas ofthe microspheres) that exhibit a coefficient of variation of greaterthan 0.05 will be referred to herein as “nonuniform” reflective layers.In various embodiments, nonuniform reflective layers may be configuredso that the percent area coverage of embedded areas of transparentmicrospheres by the reflective layers exhibits a coefficient ofvariation of greater than 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60,0.80, 1.0, 1.2, 1.4, or 2.0. In similar manner, a coefficient ofvariation of the percent area coverage of the total surface area of thetransparent microspheres by the reflective layers may be calculated. Invarious embodiments, such a coefficient of variation may be greater than0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.80, 1.0, 1.2, 1.4, or2.0. In similar manner, a coefficient of variation of thepreviously-described angular arcs occupied by the reflective layers maybe calculated. In various embodiments, such a coefficient of variationmay be greater than 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60,0.80, 1.0, 1.2, 1.4, or 2.0.

It will be appreciated that a population of nonuniform reflective layersas defined and described herein differs markedly from conventional,uniform populations of reflective layers as often described in the art.Conventional approaches (whether using transparent microspheres,prismatic elements such as cube-corners, etc.) typically seek to achieveas much uniformity in geometric parameters as possible. Ordinaryartisans will appreciate that conventional procedures in whichtransparent microspheres are partially embedded in a temporary carrier,the protruding portions of the microspheres are provided with reflectivelayers by deposition methods that are at least generally uniform over alarge scale, and a binder layer is then formed thereon, will not producenonuniform reflective layers as defined and described herein. Examplesof at least generally uniform deposition methods (i.e., methods that“blanket” a large number of protruding portions of microspheres withreflective coatings in generally uniform fashion) that would not beexpected by an ordinary artisan to provide nonuniform reflectivecoatings include e.g. vacuum deposition, vapor coating, sputter coating,electroless plating, and the like (when performed without any masking,subsequent etching, or any such action that might impose variation).Specific examples of reflective layers that exhibit such high uniformityas to seemingly exhibit a zero coefficient of variation and that thuswould not qualify as nonuniform reflective layers as defined herein,include e.g. the reflective layers pictured in U.S. Pat. Nos. 3,700,305,4,763,985, and 5,344,705.

It is thus evident that the approaches disclosed herein differ sharplyfrom conventional approaches to producing retroreflective articles. Thepresent arrangements tolerate, and even welcome, considerable variationin the shape, size, etc. of the various reflective layers, as long asacceptable overall performance (in particular, a balance betweenretroreflectivity in retroreflected light and color fidelity/vividnessin ambient light) is achieved. Furthermore, rather than requiringreflective layers to be continuous and defect-free (i.e. free ofthrough-holes), in at least some embodiments at least some of thereflective layers may comprise interruptions (e.g. holes, cracks orgaps) so that they are optically “leaky”.

Absence of Reflective Layers

Still further, in some embodiments a significant number of transparentmicrospheres may completely lack an embedded reflective layer.(Microspheres without embedded reflective layers will not be included inthe above-mentioned statistical analysis to obtain a coefficient ofvariation for the percent area coverage of the reflective layerpopulation.) That is, some methods of reflective layer formation mayleave a large number of microspheres without a reflective layer disposedthereon. Numerous transparent microspheres that lack any reflectivelayer are visible in the photograph of a Working Example samplepresented in FIG. 12; one such microsphere is identified by thereference number 37 (the small white dots that are visible in the centerof many such microspheres are optical artifacts of the microspheresthemselves.) For comparison, a randomly picked reflective-layer-bearingmicrosphere is identified by reference number 20. The presence oftransparent microspheres that lack reflective layers has been found tobe acceptable (e.g., a sufficiently high coefficient ofretroreflectivity can still be attained) in many circumstances.

FIG. 13 is a front-lit optical microphotograph (taken at a magnificationsimilar to that of FIG. 12), of the front (viewing) side of aretroreflective article (including a binder layer) of a generallysimilar type to that shown in FIG. 12. While the FIG. 13 photograph isnot quantitative, it reveals that under conditions of front-litmicroscope interrogation (which mimics a retroreflective viewingcondition with the light source fairly close to the detector),microspheres bearing reflective layers disposed thereon exhibitpronounced retroreflectivity and are clearly distinguishable frommicrospheres 37 without reflective layers disposed thereon. Furthermore,the reflective-layer-bearing microspheres 20 of FIG. 13 appear todisplay good uniformity of retroreflection even though they comprisereflective layers that vary widely in size and shape (i.e., that are ofthe general type of FIG. 12).

Thus in various embodiments, a retroreflective article may be configuredso that the transparent microspheres that comprise embedded reflectivelayers represent less than 95, 90, 80, 60, 40, 20, or even 15 percent(by number) of the total transparent microspheres present in theretroreflective article. In other embodiments, transparent microspheresthat comprise embedded reflective layers will be more than 5, 10, 20,30, 50, 70, or 80 percent of the total transparent microspheres presentin the retroreflective article. In many embodiments the transparentmicrospheres that lack embedded reflective layers will not comprise anyreflective layer disposed thereon (the presence of a “secondary”reflective layer achieved by including reflective particles in binderlayer 10, as discussed later herein, is excluded from the definition ofa reflective layer that is “disposed on” a microsphere).

In some embodiments, an embedded reflective layer 30 may comprise ametal layer, e.g. a single layer, or multiple layers, of vapor-depositedmetal (e.g. aluminum or silver). In some embodiments such a layer orlayers (or precursor to form such a layer or layers) may be depositeddirectly onto areas 25 of transparent microspheres 21 (or onto rearwardsurface of 53 of an intervening layer 50, or a rearward surface 43 of acolor layer 40, as discussed later herein). In some embodiments,portions of a previously-deposited (e.g. a continuous vapor-deposited)reflective layer may be removed (e.g. by etching) to transform the metalreflective layer into a localized, embedded reflective layer, asdiscussed in further detail later herein.

In some embodiments, an embedded reflective layer may comprise adielectric reflective layer, comprised of an optical stack of high andlow refractive index layers that combine to provide reflectiveproperties. Dielectric reflective layers are described in further detailin U.S. Patent Application Publication No. 2017/0131444, which isincorporated by reference in its entirety herein for this purpose. Inparticular embodiments, a dielectric reflective layer may be a so-calledlayer-by-layer (LBL) structure in which each layer of the optical stack(i.e., each high-index layer and each low-index layer) is itselfcomprised of a substack of multiple bilayers. Each bilayer is in turncomprised of a first sub-layer (e.g. a positively charged sub-layer) anda second sub-layer (e.g. a negatively charged sub-layer). At least onesub-layer of the bilayers of the high-index substack will compriseingredients that impart a high refractive index, while at least onesub-layer of the bilayers of the low-index substack will compriseingredients that impart a low refractive index. LBL structures, methodsof making such structures, and retroreflective articles comprisingdielectric reflective layers comprising such structures, are describedin detail in U.S. Patent Application Publication No. 2017/0276844, whichis incorporated by reference in its entirety herein. In some embodimentsa reflective layer thus may comprise multiple sublayers. In someembodiments a hybrid configuration may be used in which metal reflectivelayers and dielectric reflective layers may both be present, e.g. asdiscussed in U.S. Patent Application Publication 2017/0192142. In someembodiments a layer of a transfer stack (e.g. a selective-bonding layer303 or an embrittlement layer 302 as described elsewhere herein) mayserve as a layer of a dielectric stack.

In some embodiments, an embedded reflective layer may comprise a printedlayer (e.g. comprising a reflective material such as metallic aluminumor silver). For example, a flowable precursor comprising one or morereflectivity-imparting materials (e.g., a silver ink) may be disposed(e.g. printed) on portions 28 of areas 25 of microspheres 21 (or onlayers thereon) and then solidified into a reflective layer. If desired,a printed (or otherwise disposed) reflective layer may be heat treated(e.g. sintered) to enhance the optical properties of the reflectivelayer. In particular embodiments, a printed or coated reflective layermay further comprise particles, e.g. flakes, of reflective material(e.g. aluminum flake powder, pearlescent pigment, etc.). Variousreflective materials which may be suitable are described in U.S. Pat.Nos. 5,344,705 and 9,671,533, which are incorporated by reference intheir entirety herein.

In some embodiments, an embedded reflective layer may be a“locally-laminated” reflective layer. By a locally-laminated reflectivelayer is meant that a reflective layer is pre-made as an article (e.g.as part of a film-like or sheet-like structure) after which a local areaof the pre-made reflective layer is physically transferred (i.e.laminated) to a portion of a carrier-borne transparent microsphere. Insome embodiments a locally-laminated reflective layer will be derivedfrom a multilayer “transfer stack” that includes one or more additionallayers in addition to the reflective layer. The additional layer(s) canfacilitate the transfer of the reflective layer to the transparentmicrosphere as discussed in detail later herein. In various embodiments,some such additional layers may remain as part of the resultingretroreflective article and some may be sacrificial layers that do notremain as part of the resulting retroreflective article.

Transfer stacks (referred to as transfer articles) are described ingeneral terms in U.S. Provisional Patent Application 62/478,992, whichis incorporated by reference in its entirety herein. Locally-laminatedreflective layers of various constructions and configurations aredescribed in detail in U.S. Provisional Patent Application No.62/578,343 (e.g., in Example 2.3 (including Examples 2.3.1-2.3.3) andExample 2.4 (including Examples 2.4.1-2.4.5)), which is incorporated byreference in its entirety herein. Locally-laminated reflective layers,ways in which such layers can be produced, and ways in which suchreflective layers can be identified and distinguished from other typesof reflective layers, are also described in detail in U.S. ProvisionalPatent Application No. 62/739,506, entitled RETROREFLECTIVE ARTICLECOMPRISING LOCALLY-LAMINATED REFLECTIVE LAYERS, filed evendate herewithand incorporated by reference herein in its entirety. In general, anyreflective layer 30, e.g. of any of the above-discussed types, can bedisposed on a rearward surface of a portion 28 of an embedded area 25 ofa transparent microsphere 21 or on a rearward surface of a layer presentthereon (e.g., of an intervening layer 50 or a color layer 40 asdescribed later herein).

As shown in exemplary embodiment in FIG. 5, in some embodiments anintervening layer 50 (e.g. a transparent layer of organic polymericmaterial) may be provided so that a portion, or the entirety, of theintervening layer is rearward of a microsphere 21 and forward of atleast a portion of an embedded reflective layer 30. At least a portionof such an intervening layer 50 may thus be sandwiched betweenmicrosphere 21 and reflective layer 30, e.g. with a forward surface 52of intervening layer 50 being in contact with a rearward surface ofembedded area 25 of microsphere 21, and with a rearward surface 53 ofintervening layer 50 being in contact with forward surface 32 ofembedded reflective layer 30. In some embodiments such a layer 50 may becontinuous so as to have portions that reside on front surface 4 ofarticle 1 in addition to being present rearward of microspheres 21, asin the exemplary arrangement of FIG. 5. In other embodiments such alayer may be discontinuous (e.g., it may be a localized, embedded layer)and may only be present rearward of microspheres 21 e.g. in a similarmanner to later-described color layers 40 of FIG. 6. Furthermore, even a“continuous” layer 50 may exhibit occasional through-holes or cavitiesin places where the layer precursor did not fully wet into gaps betweenthe microspheres 21, as noted earlier.

Such an intervening layer may serve any desired function. In someembodiments it may serve as a physically-protective layer and/or achemically-protective layer (e.g. that provides enhanced abrasionresistance, resistance to corrosion, etc.). In some embodiments such alayer may serve as a bonding layer (e.g. a tie layer oradhesion-promoting layer) that is capable of being bonded to by areflective layer as discussed later herein. It will be appreciated thatsome intervening layers may serve more than one, e.g. all, of thesepurposes. In some embodiments, such an intervening layer may betransparent (specifically, it may be at least essentially free of anycolorant or the like). Organic polymeric layers (e.g. protective layers)and potentially suitable compositions thereof are described in detail inU.S. Patent Application Publication No. 2017/0276844, which isincorporated by reference in its entirety herein. In particularembodiments, such a layer may be comprised of a polyurethane material.Various polyurethane materials that may be suitable for such purposesare described e.g. in U.S. Patent Application Publication No.2017/0131444, which is incorporated by reference in its entirety herein.

As illustrated in exemplary embodiment in FIG. 6, in some embodiments atleast some of the retroreflective elements 20 may comprise at least onecolor layer 40. The term “color layer” is used herein to signify a layerthat preferentially allows passage of electromagnetic radiation in atleast one wavelength range while preferentially minimizing passage ofelectromagnetic radiation in at least one other wavelength range byabsorbing at least some of the radiation of that wavelength range. Insome embodiments a color layer will selectively allow passage of visiblelight of one wavelength range while reducing or minimizing passage ofvisible light of another wavelength range. In some embodiments a colorlayer will selectively allow passage of visible light of at least onewavelength range while reducing or minimizing passage of light ofnear-infrared (700-1400 nm) wavelength range. In some embodiments acolor layer will selectively allow passage of near-infrared radiationwhile reducing or minimizing passage of visible light of at least onewavelength range. A color layer as defined herein performswavelength-selective absorption of electromagnetic radiation by the useof a colorant (e.g. a dye or pigment) that is disposed in the colorlayer. A color layer is thus distinguished from a reflective layer (andfrom a transparent layer), as will be well understood by ordinaryartisans based on the discussions herein.

Any such color layer 40 can be arranged so that light that isretroreflected by a retroreflective element 20 passes through the colorlayer so that the retroreflected light exhibits a color imparted by thecolor layer. A color layer 40 can thus be disposed so that at least aportion of layer 40 is located between rearward surface 23 of embeddedarea 25 of transparent microsphere 21 and forward surface 32 of embeddedreflective layer 30 so that at least this portion of the color layer 40is in the retroreflective light path. Thus, a forward surface 42 ofcolor layer 40 may be in contact with a rearward surface of embeddedarea 25 of microsphere 21; and, a rearward surface 43 of color layer 40may be in contact with forward surface 32 of embedded reflective layer30. In some embodiments an above-mentioned intervening layer (e.g. atransparent layer) 50 may be present in addition to a color layer 40;such layers may be provided in any order (e.g. with the color layerforward of, or rearward of, the intervening layer) as desired. In someembodiments, a color layer 40 may serve some other function (e.g. as anadherable layer or a tie layer) in addition to imparting color to theretroreflected light.

In some embodiments a color layer 40 may be a discontinuous color layer,e.g. a localized color layer as in the exemplary embodiment shown inFIG. 6. In particular embodiments a localized color layer 40 may be anembedded color layer (with the terms localized and embedded having thesame meanings as used for reflective layers as discussed above). Thatis, an embedded color layer 40 may comprise minor edges 41 that are“buried” rather than being exposed edges. In various embodiments, alocalized color layer may exhibit an average thickness (e.g. measured atseveral locations over the extent of the color layer) of from at least0.1, 0.2, 0.5, 1, 2, 4, or 8 microns, to at most 40, 20, 10, 7, 5, 4, 3,2 or 1 microns. In some embodiments an intervening layer 50 may beprovided with colorant so that it serves as a color layer 40 (inaddition to serving any or all of the above-listed functions).

The presence of color layers (e.g. localized, embedded color layers) inat least some of the retroreflective light paths of a retroreflectivearticle can allow article 1 to comprise at least some areas that exhibitcolored retroreflected light, irrespective of the color(s) that theseareas (or any other areas of the article) exhibit in ambient(non-retroreflected) light. In some embodiments, an embedded reflectivelayer may be configured so that the entirety of the reflective layer ispositioned rearwardly of a color layer. This can ensure that incominglight cannot reach the reflective layer (nor be reflected therefrom)without passing through the color layer, regardless of the angle atwhich the light enters and exits the transparent microsphere. Sucharrangements can provide that light that is retroreflected from aretroreflective element exhibits a desired color, regardless of theentrance/exit angle of the light. Such arrangements can also enable thecolor layer to mask the reflective layer for advantageously enhancedcolor appearance in ambient (non-retroreflective) light. In otherembodiments, an embedded reflective layer may be configured so that atleast some portion of the reflective layer extends beyond a minor edgeof the color layer so that light can be reflected from the reflectivelayer without passing through the color layer. Such arrangements canprovide that retroreflected light can exhibit different colors dependingon the entrance/exit angle of the light.

The previously mentioned parameters (e.g., the angular arc occupied by alayer, and the percentage of the embedded area of the microsphere thatis covered by a layer) can be used for characterization of a localized,embedded color layer in relation to a transparent microsphere and inrelation to an embedded reflective layer with which it shares aretroreflective light path. In various embodiments, at least somelocalized, embedded color layers 40 may be disposed so that they eachoccupy an angular arc comprising less than about 190, 170, 150, 130,115, or 95 degrees. In further embodiments, at least some localized,embedded color layers may each occupy an angular arc of at least about5, 15, 40, 60, 80, 90, or 100 degrees. In various embodiments, at leastsome embedded reflective layers may be disposed so that each occupies anangular arc that is less than that of a localized, embedded color layerwith which it shares a retroreflective light path, by at least 5, 10,15, 20, 25, or 30 degrees. In other embodiments, at least some embeddedreflective layers may be disposed so that each occupies an angular arcthat is greater than that of a localized, embedded color layer withwhich it shares a retroreflective light path, by at least 5, 10, 15, 20,25 or 30 degrees.

Article 1 may be arranged to provide that the appearance of article 1 inambient (non-retroreflected) light is controlled as desired. Forexample, in the exemplary arrangement of FIG. 1 the front surface 4 ofarticle 1 is provided in part (e.g. in areas 8 of front side 2 ofarticle 1 that are not occupied by transparent microspheres 21) by avisually exposed front surface 14 of binder layer 10. In suchembodiments the appearance of front side 2 of article 1 in ambient lightmay thus be largely dominated by the color (or lack thereof) of binderlayer 10 in areas 13 of binder layer 10 that are laterally betweenmicrospheres 21. Thus in some embodiments binder layer 10 may be acolorant-loaded (e.g. pigment-loaded) binder layer. The pigment may bechosen to impart any suitable color in ambient light, e.g. fluorescentyellow, green, orange, white, black, and so on.

In some embodiments the appearance of retroreflective article 1 inambient light may be manipulated e.g. by the presence and arrangement ofone or more color layers on a front side of article 1. In someembodiments any such color layers, e.g. in combination with acolorant-loaded binder, may be configured so that the front side ofarticle 1 exhibits a desired image (which term broadly encompasses e.g.informational indicia, signage, aesthetic designs, and so on) whenviewed in ambient light. In some embodiments, article 1 may beconfigured (whether through manipulation of the embedded reflectivelayers and/or manipulation of any color layers in the retroreflectivelight path) to exhibit images when viewed in retroreflected light. Inother words, any arrangement by which the appearance of article 1 inambient light may be manipulated (e.g. by the use of a colorant-loadedbinder, the use of colorant-loaded layers on the front side 4 of article1, etc.) may be used in combination with any arrangement by which theappearance of article 1 in retroreflected light may be manipulated (e.g.by the use of color layers, e.g. localized, embedded color layers, inthe retroreflective light path).

Such arrangements are not limited to the specific exemplary combinationsdiscussed herein and/or shown in the Figures herein. Many sucharrangements are discussed in detail in U.S. Provisional PatentApplication No. 62/675,020 which is incorporated by reference herein inits entirety; it will be understood that any of the color arrangementsdiscussed in the '020 application can be used with the embeddedreflective layers disclosed herein.

Regardless of the particular color arrangement that may be used, it willbe clear based on the discussions herein that the use of embeddedreflective layers 30, particularly those that occupy covered areas 28that are relatively small percentages (e.g. less than 60%) of embeddedareas 25 of transparent microspheres 21, can allow significantlyenhanced color fidelity of a retroreflective article 1 (e.g., areflective article comprising a colorant-loaded binder layer 10) whenviewed in ambient light. In other words, in ambient light the articlemay exhibit a color that more closely matches the native color of thecolorant-loaded binder (that is, the article may exhibit a color that issimilar to that which would be exhibited by the article if the articledid not comprise any retroreflective elements).

Transfer Article

In some embodiments, a retroreflective article 1 as disclosed herein maybe provided as part of a transfer article 100 that comprisesretroreflective article 1 along with a removable (disposable) carrierlayer 110 that comprises front and rear major surfaces 111 and 112. Insome convenient embodiments, retroreflective article 1 may be built onsuch a carrier layer 110, which may be removed for eventual use ofarticle 1 as described later herein. For example, a front side 2 ofarticle 1 may be in releasable contact with a rear surface 112 of acarrier layer 110, as shown in exemplary embodiment in FIG. 7.

Retroreflective article 1 (e.g. while still a part of a transfer article100) may be coupled to any desired substrate 130, as shown in FIG. 7.This may be done in any suitable manner. In some embodiments this may bedone by the use of a bonding layer 120 that couples article 1 tosubstrate 130 with the rear side 3 of article 1 facing substrate 130.Such a bonding layer 120 can bond binder layer 10 (or any layerrearwardly disposed thereon) of article 1 to substrate 130, e.g. withone major surface 124 of bonding layer 120 being bonded to rear surface15 of binder layer 10, and with the other, opposing major surface 125 ofbonding layer 120 bonded to substrate 130. Such a bonding layer 120 maybe e.g. a pressure-sensitive adhesive (of any suitable type andcomposition) or a heat-activated adhesive (e.g. an “iron-on” bondinglayer). Various pressure-sensitive adhesives are described in detail inU.S. Patent Application Publication No. 2017/0276844, which isincorporated by reference in its entirety herein.

The term “substrate” is used broadly and encompasses any item, portionof an item, or collection of items, to which it is desired to e.g.couple or mount a retroreflective article 1. Furthermore, the concept ofa retroreflective article that is coupled to or mounted on a substrateis not limited to a configuration in which the retroreflective articleis e.g. attached to a major surface of the substrate. Rather, in someembodiments a retroreflective article may be e.g. a strip, filament, orany suitable high-aspect ratio article that is e.g. threaded, woven,sewn or otherwise inserted into and/or through a substrate so that atleast some portions of the retroreflective article are visible. In fact,such a retroreflective article (e.g. in the form of a yarn) may beassembled (e.g. woven) with other, e.g. non-retroreflective articles(e.g. non-retroreflective yarns) to form a substrate in which at leastsome portions of the retroreflective article are visible. The concept ofa retroreflective article that is coupled to a substrate thusencompasses cases in which the article effectively becomes a part of thesubstrate.

In some embodiments, substrate 130 may be a portion of a garment. Theterm “garment” is used broadly, and generally encompasses any item orportion thereof that is intended to be worn, carried, or otherwisepresent on or near the body of a user. In such embodiments article 1 maybe coupled directly to a garment e.g. by a bonding layer 120 (or bysewing, or any other suitable method). In other embodiments substrate130 may itself be a support layer to which article 1 is coupled e.g. bybonding or sewing and that adds mechanical integrity and stability tothe article. The entire assembly, including the support layer, can thenbe coupled to any suitable item (e.g. a garment) as desired. Often, itmay be convenient for carrier 110 to remain in place during the couplingof article 1 to a desired entity and to then be removed after thecoupling is complete. Strictly speaking, while carrier 110 remains inplace on the front side of article 1, the areas 24 of transparentmicrospheres 21 will not yet be air-exposed and thus the retroreflectiveelements 20 may not yet exhibit the desired level of retroreflectivity.However, an article 1 that is detachably disposed on a carrier 110 thatis to be removed for actual use of article 1 as a retroreflector, willstill be considered to be a retroreflective article as characterizedherein.

Methods of Making

In some convenient embodiments, a retroreflective article 1 can be madeby starting with a disposable carrier layer 110. Transparentmicrospheres 21 can be partially (and releasably) embedded into carrierlayer 110 to form a substantially mono-layer of microspheres. For suchpurposes, in some embodiments carrier layer 110 may convenientlycomprise e.g. a heat-softenable polymeric material that can be heatedand the microspheres deposited thereonto in such manner that theypartially embed therein. The carrier layer can then be cooled so as toreleasably retain the microspheres in that condition for furtherprocessing.

Typically, the microspheres as deposited are at least slightly laterallyspaced apart from each other although occasional microspheres may be inlateral contact with each other. The pattern (that is, the packingdensity or proportional area coverage) of microspheres as deposited onthe carrier will dictate their pattern in the final article. In variousembodiments, the microspheres may be present on the final article at apacking density of at least 30, 40, 50, 60 or 70 percent (whether overthe entire article, or in microsphere-containing macroscopic areas ofthe article). In further embodiments, the microspheres may exhibit apacking density of at most 80, 75, 65, 55 or 45 percent (noting that thetheoretical maximum packing density of monodisperse spheres on a planeis in the range of approximately 90 percent). In some embodiments themicrospheres may be provided in a predetermined pattern, e.g. by usingthe methods described in U.S. Patent Application Publication2017/0293056, which is incorporated by reference herein in its entirety.

In various embodiments the microspheres 21 may be partially embedded incarrier 110 e.g. to about 20 to 50 percent of the microspheres'diameter. The areas 25 of microspheres 21 that are not embedded in thecarrier protrude outward from the carrier so that they can subsequentlyreceive reflective layer 30 and binder layer 10 (and any other layers asdesired). These areas 25 (which will form the embedded areas 25 of themicrospheres in the final article) will be referred to herein asprotruding areas of the microspheres during the time that themicrospheres are disposed on the carrier layer in the absence of abinder layer. In customary manufacturing processes, there may be somevariation in how deeply the different microspheres are embedded intocarrier 110, which may affect the size and/or shape of the reflectivelayers that are deposited onto portions of the protruding surfaces ofthe different microspheres.

An exemplary carrier layer comprising transparent microspheres thereonis described in the Working Examples herein as a Temporary Bead Carrier.Further details of suitable carrier layers, methods of temporarilyembedding transparent microspheres in carrier layers, and methods ofusing such layers to produce retroreflective articles, are disclosed inU.S. Patent Application Publication No. 2017/0276844.

After microspheres 21 are partially embedded in carrier 110, reflectivelayers (that will become embedded reflective layers after formation ofbinder layer 10) can be formed on portions of protruding areas 25 of atleast some of the microspheres (again, protruding areas 25 will becomeembedded areas after binder layer 10 is formed). A reflective layer maybe achieved by any method that can form a reflective layer (or areflective layer precursor that can solidify e.g. by drying, curing, orthe like to form the actual reflective layer) in such manner that thereflective layer is embedded as defined and described herein.

In many convenient embodiments a deposition process may be arranged toprovide that a reflective layer is formed only on portions of protrudingareas 25 of microspheres 21 and not, for example, on the surface 112 ofthe carrier 110. For example, a contact-transfer process (e.g.flexographic printing, or lamination) may be used in which a reflectivelayer (or precursor) is brought into contact with protruding areas ofthe microspheres so that the reflective layer transfers to portions ofthe protruding areas of the microspheres without transferring to thesurface of the carrier to any significant extent. Any such process maybe controlled so that the reflective layer (or precursor) is notdisposed on the entirety of the protruding area 25 of a microsphere 21.That is, in some instances the process may be carried out so that areflective layer or precursor is transferred only to an outermostportion of the protruding area 25 of microsphere 21 (which outermostportion will become the rearmost portion of embedded area 25 ofmicrosphere 21 in the final article). In some instances a reflectivelayer may be transferred to a portion of the embedded area that isgreater than the portion to be occupied by the reflective layer in thefinal article, after which some part of the reflective layer may beremoved to leave only the desired area coverage.

By way of a specific example with reference to FIG. 3, a microsphere 21may be disposed on a carrier 110 so that approximately 40% of themicrosphere diameter is embedded in the carrier. Thus, an area 25 ofmicrosphere 21 will protrude outward from a major surface of the carrierlayer 110, to a maximum distance that corresponds to approximately 60%of the diameter of the microsphere. A reflective layer formation (e.g.transfer) process may be performed so that the reflective layer onlycovers outermost portion 28 (e.g. occupying an angular arc ofapproximately 80-85 degrees) of protruding area 25 of the microsphere.After the reflective layer formation process is complete, a remainingportion 27 of protruding area 25 of microsphere 21 will not comprise areflective layer 30 thereon. Upon formation of a binder layer 10, aretroreflective element 20 will be formed comprising a microsphere 21and reflective layer 30 arranged in the general manner depicted in FIG.3. That is, reflective layer 30 will cover only a generally rearwardportion 28 of embedded area 25 of microsphere 21, and will not cover theremaining (e.g. forward) portion 27 of embedded area 25.

Reflective layers 30 may be disposed on portions of protruding areas 25of (carrier-borne) transparent microspheres 21 by any suitable method orcombinations of methods. This may be done e.g. by vapor deposition e.g.of a metal layer such as aluminum or silver, by deposition of numeroushigh and low refractive index layers to form a dielectric reflectivelayer, by printing (e.g. flexographic printing) or otherwise disposing aprecursor comprising a reflective additive and then solidifying theprecursor, by physically transferring (e.g. laminating) a pre-madereflective layer, and so on. In particular embodiments, a printable inkmay comprise a precursor additive that can be transformed into areflective material. For example, an ink might comprise silver in a form(e.g. such as silver cations or as an organometallic silver compound)that, after being printed onto desired areas, can be chemically reacted(e.g. reduced) to form metallic silver that is reflective. Commerciallyavailable printable silver inks include e.g. PFI-722 Conductive FlexoInk (Novacentrix, Austin, Tex.) and TEC-PR-010 ink (Inktec, Gyeonggi-do,Korea).

Thus in some embodiments, reflective layers 30 may be provided byprinting a reflective ink or ink precursor on portions of protrudingareas of carrier-borne transparent microspheres. Processes of thisgeneral type, in which a flowable precursor is deposited only ontocertain portions of protruding areas of microspheres, will becharacterized herein as “printing” processes. This will be contrastedwith a “coating” process in which a material is deposited not only onprotruding areas of the microspheres but also on the surface of thecarrier, between the microspheres. In some convenient embodiments, suchprinting may comprise flexographic printing. Other methods of printingmay be used as an alternative to flexographic printing. Such methods mayinclude e.g. pad printing, soft lithography, gravure printing, offsetprinting, and the like. In general, any deposition method (e.g. inkjetprinting) may be used, as long as the process conditions and the flowproperties of the reflective layer precursor are controlled so that theresulting reflective layer is an embedded (e.g. localized) reflectivelayer. It will be appreciated that whatever the method used, it may beadvantageous to control the method so that the precursor is deposited ina very thin layer (e.g. a few microns or less) and at an appropriateviscosity, to provide that the precursor remains at least substantiallyin the area in which it was deposited. Such arrangements may ensurethat, for example, the resulting reflective layer occupies a desiredportion 28 of embedded area 25 in the manner described above. It willalso be appreciated that some deposition methods may provide areflective layer in which the thickness may vary somewhat from place toplace. In other words, the rearward major surface 33 of a reflectivelayer 30 may not necessarily be exactly congruent with the major forwardsurface 32 of the reflective layer. However, at least some amount ofvariation of this type (as may occur e.g. with flexographic printing)has been found to be acceptable in the present work.

In some embodiments, a localized, embedded reflective layer 30 may beprovided e.g. by forming a reflective layer (e.g. by vapor coating of ametal, or by printing or coating a reflective ink) onto a carrier andmicrospheres thereon, and then removing (e.g. by etching) the reflectivelayer selectively from the surface of the carrier and from portions 27of protruding areas 25 of the microspheres (before any binder layer isbeen formed) to leave localized reflective layers in place on themicrospheres. In some particular embodiments of this type, anetch-resistant material (often referred to as a “resist”) may be applied(e.g. by printing) on portions of a reflective layer that are atop theprotruding areas of the microspheres, but is not applied to otherportions of the microsphere-residing reflective layer and is not appliedto the reflective layer that resides on the carrier surface. An etchantcan then be applied that removes the reflective layer except theportions thereof that are protected by the resist. Such methods aredescribed in further detail in U.S. Provisional Patent Application No.62/578,343, which is incorporated by reference herein.

In some embodiments a localized, embedded reflective layer 30 may beprovided by a local lamination process. A local lamination process isone in which a local area of a pre-made reflective layer is transferredto portion of a protruding area of a transparent microsphere. Duringthis process, the local area of the reflective layer is detached from(breaks free of) a region of the reflective layer that previously (inthe pre-made reflective layer before lamination) laterally surroundedthe transferred area. The laterally-surrounding region of the reflectivelayer from which the local area was detached is not transferred to themicrosphere (or to any portion of the resulting article) but rather isremoved from the vicinity of the microsphere (e.g., along with other,sacrificial layers of a multilayer transfer stack of which the pre-madereflective layer was a part). Local lamination methods are described indetail in the aforementioned U.S. Provisional Patent Application No.62/739,506, entitled RETROREFLECTIVE ARTICLE COMPRISINGLOCALLY-LAMINATED REFLECTIVE LAYERS, filed evendate herewith andincorporated by reference herein in its entirety. Several of the WorkingExamples (e.g. Examples 2.3 and 2.4) in the present application alsoillustrate the use of local lamination methods.

In some embodiments, a carrier layer bearing transparent microspheresand any desired layers may be provided as an intermediate article, inthe absence of any binder layer, as discussed in detail below. In otherembodiments, after formation of the reflective layers (and deposition ofany intervening layer 50 and/or color layer 40) is carried out, a binderprecursor (e.g., a mixture or solution of binder layer components) canbe applied to microsphere-bearing carrier layer 110. The binderprecursor may be disposed, e.g. by coating, onto the microsphere-loadedcarrier layer and then hardened to form a binder layer, e.g. acontinuous binder layer. The binder may be of any suitable composition,e.g. it may be formed from a binder precursor that comprises anelastomeric polyurethane composition along with any desired additives,etc. Binder compositions, methods making binders from precursors, etc.,are described in U.S. Patent Application Publication Nos. 2017/0131444and 2017/0276844, which are incorporated by reference in their entiretyherein.

In general, binder layer 10 is configured to support transparentmicrospheres 21 and is typically a continuous, fluid-impermeable,sheet-like layer. In various embodiments, binder layer 10 may exhibit anaverage thickness of from 1 to 250 micrometers. In further embodiments,binder layer 10 may exhibit an average thickness of from 30 to 150micrometers. Binder layer 10 may include polymers that contain unitssuch as urethane, ester, ether, urea, epoxy, carbonate, acrylate,acrylic, olefin, vinyl chloride, amide, alkyd, or combinations thereof.A variety of organic polymer-forming reagents can be used to make thepolymer. Polyols and isocyanates can be reacted to form polyurethanes;diamines and isocyanates can be reacted to form polyureas; epoxides canbe reacted with diamines or diols to form epoxy resins, acrylatemonomers or oligomers can be polymerized to form polyacrylates; anddiacids can be reacted with diols or diamines to form polyesters orpolyamides. Examples of materials that may be used in forming binderlayer 10 include for example: Vitel™ 3550 available from Bostik Inc.,Middleton, Mass.; Ebecryl™ 230 available from UBC Radcure, Smyrna, Ga.;Jeffamine™ T-5000, available from Huntsman Corporation, Houston, Tex.;CAPA 720, available from Solvay Interlox Inc., Houston Tex.; andAcclaim™ 8200, available from Lyondell Chemical Company, Houston, Tex.

In some embodiments binder layer 10 may be at least generally visiblytransmissive (e.g. transparent). In many convenient embodiments binderlayer 10 may comprise one or more colorants. In particular embodiments abinder may comprise one or more fluorescent pigments. Suitable colorants(e.g. pigments) may be chosen e.g. from those listed in the above-cited'444 and '844 Publications.

In some embodiments, binder layer 10 may contain reflective particles179, e.g. flakes, of reflective material (e.g. nacreous or pearlescentmaterial), so that at least a portion of binder layer 10 that isadjacent to transparent microsphere 21 can function as a secondaryreflective layer 180 as depicted in exemplary embodiment in FIG. 7. By a“secondary” reflective layer is meant a layer of binder layer 10 thatserves to enhance the performance of a retroreflective element above theperformance provided by the embedded “primary” reflective layer 30 thatcovers an area 28 of a transparent microsphere. A secondary reflectivelayer 180 by definition operates adjacent a portion 27 of embedded area25 of the transparent microsphere 21 that is not covered by the embeddedreflective layer 30. Such a secondary reflective layer (which may notnecessarily have a well-defined rearward boundary) may provide at leastsome retroreflection due to the aggregate effects of the reflectiveparticles that are present in the layer. It will be appreciated thatsuch a secondary reflective layer may not necessarily provide the sameamount and/or quality of retroreflection that is provided by an embeddedreflective layer 30. However, such a secondary reflective layer mayprovide that, for example, areas 27 of transparent microspheres, thatare not covered by embedded reflective layers 30, may neverthelessexhibit some retroreflectivity. Thus, in some embodiments, the embeddedreflective layers 30 may act as primary reflectors that provideretroreflection e.g. at light-incidence angles that are generallyaligned with the front-rear axis of the article, while the secondaryreflective layers 180 may provide at least some secondaryretroreflection e.g. at high or glancing angles of incident light.Furthermore, this may be done while still preserving at least asignificant portion of the previously-described enhanced color fidelitythat is enabled by the absence of any embedded reflective layers 30 inportions 27 of embedded areas 25 of microspheres 21.

To achieve such effects, in various embodiments binder layer 10 may beloaded with reflective particles 179 at a loading of at least 0.05,0.10, 0.20, 0.50, 1.0, 2.0, or 5.0 weight percent. In furtherembodiments, binder layer may be loaded with reflective particles at aloading of at most 30, 20, 10, 6, 4, 2.0, 1.5, 0.8, 0.4, 0.3, or 0.15weight percent. (All such loadings are on a dry-solids basis rather thanincluding any liquid or volatile material that does not remain in thebinder layer.) In various embodiments, the reflective particles maycomprise an average particle size (diameter or effective diameter) of atleast 5 microns; in further embodiments the reflective particles maycomprise an average particle size of at most about 200 microns. It isnoted that in many embodiments the reflective particles may be e.g.flake-like, with a high aspect ratio of e.g. greater than 2.0, 4.0, or8.0. In such cases, the reflective particles may comprise, on average, alongest dimension of from at least 5 microns to at most 200 microns.

In some embodiments it may be particularly advantageous that the averageparticle size (or the average longest dimension, in the case of highaspect ratio particles) of the reflective particles in the binder bechosen to be smaller than the average particle size (diameter) of thetransparent microspheres. Thus in various embodiments the averageparticle size of the reflective particles in the binder may be no morethan 40%, 20%, 10%, or 5%, of the average particle size of thetransparent microspheres.

Suitable reflective particles may be chosen from e.g. nacreous pigmentflakes such as BiOCl, TiO₂-coated mica, oxide-coated glass flakes,hexagonal PbCO₃ particles, oxide-coated fluorphlogopite platelets andcrystalline guanine platelets (obtained e.g. from fish scales). Invarious particular embodiments, secondary reflective layers 180resulting from the presence of reflective particles 179 in binder layer10, may be used in combination with embedded reflective layers 30 thatexhibit an area coverage (i.e., that comprise a covered portion 28 of anembedded area 25) of less than 50, 40, 30, 20 or even 10 percent). Invarious embodiments, such secondary reflective layers may be used incombination with embedded reflective layers that exhibit an angular arcof less than 80, 60, 50, 40, 30, 20 or 10 degrees. In some embodiments,binder layer 10 will comprise less than 8.0, 7.5, 7.0, 6.0, 5.0, 4.0,2.0, 1.5, 0.8, 0.4, 0.3, or 0.15 weight percent (total dry solids basis)nacreous reflective particles of any type (e.g. BiOCl, PbCO₃, guanine,etc.). Arrangements comprising primary and secondary reflective layersare discussed in further detail in U.S. Provisional Patent Application62/739,529; entitled “RETROREFLECTIVE ARTICLE COMPRISING RETROREFLECTIVEELEMENTS COMPRISING PRIMARY REFLECTIVE LAYERS AND SECONDARY REFLECTIVELAYERS”, filed evendate herewith and incorporated by reference herein inits entirety.

In some embodiments, any other layer may be provided rearwardly behindbinder layer 10 (e.g. between binder layer 10 and a bonding (e.g.pressure-sensitive adhesive) layer 120, or between reflective layer 30and binder layer 10, for any purpose. Thus in some embodiments e.g. inwhich binder layer 10 is at least partially visibly transmissive, alayer may be provided that includes an image that is visible, throughbinder layer 10, in ambient light. In a variation of such an approach,an image may be printed on the rearward surface 124 of binder layer 10.In some embodiments, a layer bearing a visible image can be printedbehind reflective layer 30 prior to the application of binder layer 10.

Intermediate Article

Discussions herein have primarily concerned articles of the generaltypes shown e.g. in FIGS. 1 and 5 (including a binder layer, and in theform of e.g. a transfer article). However, in some embodiments thearrangements disclosed herein, comprising embedded reflective layers 30or their equivalents, may be provided in an article that does notcomprise a binder layer. Such an article will be termed an“intermediate” article for convenience of description. As shown inexemplary embodiment in FIG. 8, in embodiments of this type, anintermediate article 1000 may take the form of a carrier layer 110bearing transparent microspheres 21 on a first surface 112 thereof,without any binder layer being present. (However, transparentmicrospheres 21 may be protected e.g. by a removable cover film providedon the microsphere-bearing side of the carrier layer, if desired.) Suchan intermediate article will comprise at least some transparentmicrospheres 21 that comprise protruding areas 25 on portions 28 ofwhich are disposed reflective layers 30. Strictly speaking thesereflective layers 30 will not be “embedded” layers until a binder layer10 is present. So, in embodiments of this particular type, suchreflective layers will be equivalently characterized as being “isolated”reflective layers, meaning that they cover a portion, but do not coverthe entirety, of the protruding areas 25 of the microspheres. Thevarious characterizations of embedded reflective layers in terms ofpercent area coverage, angular arcs, and so on, will be understood to beapplicable in similar manner to isolated reflective layers inintermediate articles in which a binder layer has not yet been disposedto form the final article.

In some embodiments, an intermediate article may comprise an interveninglayer 50 of the general type described elsewhere herein. Other layers(e.g. color layers 40, bonding layers 120, and/or a substrate 130) maybe included in the intermediate article as desired. Any such carrierlayer 110 as disclosed herein may be disposable, which term broadlyencompasses carrier layers that are removed before actual use of theretroreflective article, after which the carrier layer is disposed,recycled, repurposed, and so on.

An intermediate article, comprising transparent microspheres withisolated reflective layers thereon, can be further processed as desired.In some embodiments, a binder layer e.g. comprising any desired colorantmay be disposed onto the microsphere-bearing carrier layer in order toform an article 1. Intermediate articles of any suitable configurationmay be shipped to customers who may, for example, dispose binder layersthereon to form customized articles.

Discussions herein have primarily concerned retroreflective articles inwhich areas 24 of microspheres 21 that are exposed (i.e., that protrude)forwardly of binder 10, are exposed to an ambient atmosphere (e.g., air)in the final retroreflective article as used. In other embodiments, theexposed areas 24 of microspheres 21 may be covered by, and/or residewithin, a cover layer that is a permanent component of article 1. Sucharticles will be termed encapsulated-lens retroreflective articles. Insuch cases, the transparent microspheres may be chosen to comprise arefractive index that performs suitably in combination with therefractive index of the cover layer. In various embodiments, in anencapsulated-lens retroreflective article, the microspheres 21 maycomprise a refractive index (e.g. obtained through the composition ofthe material of the microspheres, and/or through any kind of surfacecoating present thereon) that is at least 2.0, 2.2, 2.4, 2.6, or 2.8. Insome embodiments, a cover layer of an encapsulated-lens retroreflectivemay comprise sublayers. In such cases, the refractive indices of themicrospheres and the sublayers may be chosen in combination.

In some embodiments, such a cover layer may be a transparent layer. Inother embodiments, the entirety, or selected regions, of a cover layermay be colored (e.g. may include one or more colorants) as desired. Insome embodiments, a cover layer may take the form of a pre-existing filmor sheet that is disposed (e.g. laminated) to at least selected areas ofthe front side of article 1. In other embodiments, a cover layer may beobtained by printing, coating or otherwise depositing a cover layerprecursor onto at least selected areas of the front side of article 1,and then transforming the precursor into the cover layer.

As noted earlier herein, in some embodiments a color layer 40 mayperform wavelength-selective absorption of electromagnetic radiation atat least somewhere in a range that includes visible light, infraredradiation, and ultraviolet radiation, by the use of a colorant that isdisposed in the color layer. The term colorant broadly encompassespigments and dyes. Conventionally, a pigment is considered to be acolorant that is generally insoluble in the material in which thecolorant is present and a dye is considered to be a colorant that isgenerally soluble in the material in which the colorant is present.However, there may not always be a bright-line distinction as to whethera colorant behaves as a pigment or a dye when dispersed into aparticular material. The term colorant thus embraces any such materialregardless of whether, in a particular environment, it is considered tobe a dye or a pigment. Suitable colorants are described and discussed indetail in the aforementioned U.S. Provisional Patent Application62/675,020.

Transparent microspheres 21 as used in any article disclosed herein maybe of any suitable type. The term “transparent” is generally used torefer to a body (e.g. a glass microsphere) or substrate that transmitsat least 50% of electromagnetic radiation at a selected wavelength orwithin a selected range of wavelengths. In some embodiments, thetransparent microspheres may transmit at least 75% of light in thevisible light spectrum (e.g., from about 400 nm to about 700 nm); insome embodiments, at least about 80%; in some embodiments, at leastabout 85%; in some embodiments, at least about 90%; and in someembodiments, at least about 95%. In some embodiments, the transparentmicrospheres may transmit at least 50% of radiation at a selectedwavelength (or range) in the near infrared spectrum (e.g. from 700 nm toabout 1400 nm). In various embodiments, transparent microspheres may bemade of e.g. inorganic glass, and/or may have a refractive index of e.g.from 1.7 to 2.0. (As noted earlier, in encapsulated-lens arrangements,the transparent microspheres may be chosen to have a higher refractiveindex as needed.) In various embodiments, the transparent microspheresmay have an average diameter of at least 20, 30, 40, 50, 60, 70, or 80microns. In further embodiments, the transparent microspheres may havean average diameter of at most 200, 180, 160, 140 120, 100, 80, or 60microns. The vast majority (e.g. at least 90% by number) of themicrospheres may be at least generally, substantially, or essentiallyspherical in shape. However, it will be understood that microspheres asproduced in any real-life, large-scale process may comprise a smallnumber of microspheres that exhibit slight deviations or irregularitiesin shape. Thus, the use of the term “microsphere” does not require thatthese items must be e.g. perfectly or exactly spherical.

U.S. Patent Application Publication Nos. 2017/0276844 and 2017/0293056,which are incorporated by reference in their entirety herein, discussmethods of characterizing retroreflectivity according to e.g. acoefficient of retroreflectivity (R_(A)). In various embodiments, atleast selected areas of retroreflective articles as disclosed herein mayexhibit a coefficient of retroreflectivity, measured (at 0.2 degreesobservation angle and 5 degrees entrance angle) in accordance with theprocedures outlined in these Publications, of at least 50, 100, 200,250, 350, or 450 candela per lux per square meter. In some embodiments,the R_(A) may be highest when measured at a “head-on” entrance angle(e.g. 5 degrees). In other embodiments, the R_(A) may be highest whenmeasured at a “glancing” entrance angle (e.g. 50 degrees, or even 88.76degrees).

In various embodiments, retroreflective articles as disclosed herein maymeet the requirements of ANSI/ISEA 107-2015 and/or ISO 20471:2013. Inmany embodiments, retroreflective articles as disclosed herein mayexhibit satisfactory, or excellent, wash durability. Such washdurability may be manifested as high R_(A) retention (a ratio betweenR_(A) after wash and R_(A) before wash) after numerous (e.g. 25) washcycles conducted according to the method of ISO 6330 2A, as outlined inU.S. Patent Application Publication No. 2017/0276844. In variousembodiments, a retroreflective article as disclosed herein may exhibit apercent of R_(A) retention of at least 30%, 50%, or 75% after 25 suchwash cycles. In various embodiments, a retroreflective article asdisclosed herein may exhibit any of these retroreflectivity-retentionproperties in combination with an initial R_(A) (before washing) of atleast 100 or 330 candela per lux per square meter, measured as notedabove.

A retroreflective article as disclosed herein may be used for anydesired purpose. In some embodiments, a retroreflective article asdisclosed herein may be configured for use in or with a system thatperforms e.g. machine vision, remote sensing, surveillance, or the like.Such a machine vision system may rely on, for example, one or morevisible and/or near-infrared (IR) image acquisition systems (e.g.cameras) and/or radiation or illumination sources, along with any otherhardware and software needed to operate the system. Thus in someembodiments, a retroreflective article as disclosed herein (whether ornot it is mounted on a substrate) may be a component of, or work inconcert with, a machine vision system of any desired type andconfiguration. Such a retroreflective article may, for example, beconfigured to be optically interrogated (whether by a visual-wavelengthor near-infrared camera, e.g. at a distance of up to several meters, oreven up to several hundred meters) regardless of the ambient lightconditions. Thus in various embodiments, such a retroreflective articlemay comprise retroreflective elements configured to collectively exhibitany suitable image(s), code(s), pattern, or the like, that allowinformation borne by the article to be retrieved by a machine visionsystem. Exemplary machine vision systems, ways in which retroreflectivearticles can be configured for use in such systems, and ways in whichretroreflective articles can be characterized with specific regard totheir suitability for such systems, are disclosed in U.S. ProvisionalPatent Application No. 62/536,654, which is incorporated by reference inits entirety herein.

In some embodiments, embedded reflective layers 30, color layers 40,and/or a cover layer (e.g. in the particular embodiment in which anarticle is an encapsulated-lens retroreflective article) may be providedin various macroscopic areas of a retroreflective article rather thancollectively occupying the entirety of the article. Such arrangementscan allow images to be visible in retroreflected light (whether suchimages stand out by way of increased retroreflectivity and/or by way ofan enhanced color). In some embodiments, such images may be achievede.g. by performing patterned deposition of the reflective layers. Asnoted earlier herein, in various embodiments a retroreflective articleas disclosed herein may be configured to exhibit images when viewed inretroreflected light, to exhibit images when viewed in ambient light, orboth. If both are present, the images when viewed in ambient light maybe generally the same as those when viewed in retroreflected light (e.g.an article may convey the same information under both conditions); orthe images may be different (e.g. so that different information isconveyed in ambient light versus in retroreflected light).

Various components of retroreflective articles (e.g. transparentmicrospheres, binder layers, reflective layers, etc.), methods of makingsuch components and of incorporating such components intoretroreflective articles in various arrangements, are described e.g. inU.S. Patent Application Publication Nos. 2017/0131444, 2017/0276844, and2017/0293056, and in U.S. Provisional Patent Application No. 62/578,343,all of which are incorporated by reference in their entirety herein.

It will be appreciated that retroreflective elements comprising embeddedreflective layers as disclosed herein, can be used in anyretroreflective article of any suitable design and for any suitableapplication. In particular, it is noted that the requirement of thepresence of retroreflective elements comprising transparent microspheres(along with one or more color layers, reflective layers, etc.) does notpreclude the presence, somewhere in the article, of otherretroreflective elements (e.g. so-called cube-corner retroreflectors)that do not comprise transparent microspheres.

Although discussions herein have mainly concerned use of theherein-described retroreflective articles with garments and like items,it will be appreciated that these retroreflective articles can find usein any application, as mounted to, or present on or near, any suitableitem or entity. Thus, for example, retroreflective articles as disclosedherein may find use in pavement marking tapes, road signage, vehiclemarking or identification (e.g. license plates), or, in general, inreflective sheeting of any sort. In various embodiments, such articlesand sheeting comprising such articles may present information (e.g.indicia), may provide an aesthetic appearance, or may serve acombination of both such purposes.

LIST OF EXEMPLARY EMBODIMENTS

Embodiment 1 is a retroreflective article comprising: a binder layer;and, a plurality of retroreflective elements spaced over a length andbreadth of a front side of the binder layer, each retroreflectiveelement comprising a transparent microsphere partially embedded in thebinder layer so as to exhibit an embedded surface area of thetransparent microsphere; wherein the article is configured so that atleast some of the retroreflective elements each comprise a reflectivelayer that is embedded between the transparent microsphere and thebinder layer and wherein at least some of the embedded reflective layersof the retroreflective article are localized reflective layers; whereineach localized, embedded reflective layer covers a portion of theembedded surface area of the transparent microsphere that is less thanthe entirety of the embedded surface area of the transparentmicrosphere.

Embodiment 2 is the retroreflective article of embodiment 1 wherein thearticle is configured so that at least 60% of the embedded reflectivelayers of the retroreflective article are localized reflective layers.

Embodiment 3 is the retroreflective article of any of embodiments 1-2wherein the article is configured so that at least some of thelocalized, embedded reflective layers each cover a portion of theembedded surface area of the transparent microsphere that is less than60% of the embedded surface area of the transparent microsphere.

Embodiment 4 is the retroreflective article of any of embodiments 1-3wherein the article is configured so that at least some of thelocalized, embedded reflective layers each cover a portion of theembedded surface area of the transparent microsphere in such manner thatthe covered portion of the embedded surface area of the transparentmicrosphere is less than 50% of a total surface area of the transparentmicrosphere.

Embodiment 5 is the retroreflective article of any of embodiments 1-3wherein the article is configured so that at least some of thelocalized, embedded reflective layers each cover a portion of theembedded surface area of the transparent microsphere in such manner thatthe covered portion of the embedded surface area of the transparentmicrosphere is less than 25% of a total surface area of the transparentmicrosphere.

Embodiment 6 is the retroreflective article of any of embodiments 1-5wherein the localized, embedded reflective layers each occupy an angulararc of at most 180 degrees.

Embodiment 7 is the retroreflective article of any of embodiments 1-5wherein at least some of the localized, embedded reflective layersoccupy an angular arc of, on average, from greater than 5 degrees to atmost 50 degrees.

Embodiment 8 is the retroreflective article of any of embodiments 1-7wherein the article is configured to comprise at least some transparentmicrospheres that do not comprise reflective layers disposed thereon,and wherein the transparent microspheres that comprise embeddedreflective layers make up from at least 5 percent to at most 95 percentof the total number of transparent microspheres of the retroreflectivearticle.

Embodiment 9 is the retroreflective article of any of embodiments 1-8wherein at least some of the retroreflective elements comprise anintervening layer at least a portion of which is disposed between thetransparent microsphere and the binder layer so that a localized,embedded reflective layer is positioned between the intervening layerand the binder layer.

Embodiment 10 is the retroreflective article of any of embodiments 1-9wherein the binder layer comprises a colorant.

Embodiment 11 is the retroreflective article of any of embodiments 1-10wherein at least some of the retroreflective elements comprise alocalized layer that is an embedded layer that is embedded between thetransparent microsphere and the localized, embedded reflective layer.

Embodiment 12 is the retroreflective article of any of embodiments 1-11wherein at least some of the localized, embedded reflective layerscomprise a metal reflecting layer.

Embodiment 13 is the retroreflective article of any of embodiments 1-12wherein at least some of the localized, embedded reflective layerscomprise a reflecting layer that is a dielectric reflective layercomprising alternating high and low refractive index sublayers.

Embodiment 14 is the retroreflective article of any of embodiments 1-13wherein the article exhibits an initial coefficient of retroreflectivity(R_(A), measured at 0.2 degrees observation angle and 5 degrees entranceangle), in the absence of being exposed to a wash cycle, of at least 100candela per lux per square meter.

Embodiment 15 is the retroreflective article of any of embodiments 1-14wherein the article exhibits a coefficient of retroreflectivity (R_(A),measured at 0.2 degrees observation angle and 5 degrees entrance angle)after 25 wash cycles, that is at least 30% of an initial coefficient ofretroreflectivity in the absence of being exposed to a wash cycle.

Embodiment 16 is the retroreflective article of any of embodiments 1-15wherein the binder layer comprises less than 7.0 wt. percent nacreousreflective particles.

Embodiment 17 is the retroreflective article of any of embodiments 1-15wherein the binder layer comprises less than 4.0 wt. percent nacreousreflective particles.

Embodiment 18 is the retroreflective article of any of embodiments 1-15wherein the binder layer comprises less than 2.0 wt. percent nacreousreflective particles.

Embodiment 19 is the retroreflective article of any of embodiments 1-15wherein the binder layer comprises less than 0.5 wt. percent nacreousreflective particles.

Embodiment 20 is the retroreflective article of any of embodiments 1-15wherein the binder layer comprises from 0.2 wt. % to 7.5 wt. % nacreousreflective particles.

Embodiment 21 is the retroreflective article of any of embodiments 1-20wherein the article is configured so that at least some of thelocalized, embedded reflective layers each cover a portion of theembedded surface area of the transparent microsphere that is less than40% of the embedded surface area of the transparent microsphere.

Embodiment 22 is the retroreflective article of any of embodiments 1-20wherein the article is configured so that at least some of thelocalized, embedded reflective layers each cover a portion of theembedded surface area of the transparent microsphere that is less than20% of the embedded surface area of the transparent microsphere.

Embodiment 23 is the retroreflective article of any of embodiments 1-22wherein the article is configured to comprise at least some transparentmicrospheres that do not comprise reflective layers disposed thereon,and wherein the transparent microspheres that comprise embeddedreflective layers make up from at least 5 percent to at most 80 percentof the total number of transparent microspheres of the retroreflectivearticle.

Embodiment 24 is the retroreflective article of any of embodiments 1-22wherein the article is configured to comprise at least some transparentmicrospheres that do not comprise reflective layers disposed thereon,and wherein the transparent microspheres that comprise embeddedreflective layers make up from at least 5 percent to at most 60 percentof the total number of transparent microspheres of the retroreflectivearticle.

Embodiment 25 is the retroreflective article of any of embodiments 1-24wherein the embedded reflective layers are nonuniform reflective layersconfigured so that the percent area coverage of embedded surface areasof transparent microspheres by the embedded reflective layers exhibits acoefficient of variation greater than 0.05.

Embodiment 26 is the retroreflective article of any of embodiments 1-24wherein the embedded reflective layers are nonuniform reflective layersconfigured so that the percent area coverage of embedded surface areasof transparent microspheres by the embedded reflective layers exhibits acoefficient of variation greater than 0.10.

Embodiment 27 is the retroreflective article of any of embodiments 1-24wherein the embedded reflective layers are nonuniform reflective layersconfigured so that the percent area coverage of embedded surface areasof transparent microspheres by the embedded reflective layers exhibits acoefficient of variation greater than 0.20.

Embodiment 28 is the retroreflective article of any of embodiments 1-27wherein at least 50% of the retroreflective elements each comprise areflective layer that is embedded between the transparent microsphereand the binder layer.

Embodiment 29 is the retroreflective article of any of embodiments 1-27wherein at least 80% of the retroreflective elements each comprise areflective layer that is embedded between the transparent microsphereand the binder layer.

Embodiment 30 is a transfer article comprising the retroreflectivearticle of any of embodiments 1-29 and a disposable carrier layer onwhich the retroreflective article is detachably disposed with at leastsome of the transparent microspheres in contact with the carrier layer.

Embodiment 31 is a substrate comprising the retroreflective article ofany of embodiments 1-29, wherein the binder layer of the retroreflectivearticle is coupled to the substrate with at least some of theretroreflective elements of the retroreflective article facing away fromthe substrate. Embodiment 32 is the substrate of embodiment 31 whereinthe substrate is a fabric of a garment. Embodiment 33 is the substrateof embodiment 31 wherein the substrate is a support layer that supportsthe retroreflective article and that is configured to be coupled to afabric of a garment.

Embodiment 34 is an intermediate article comprising: a disposablecarrier layer with a major surface; a plurality of transparentmicrospheres partially embedded in the disposable carrier layer so thatthe transparent microspheres exhibit protruding surface areas; andwherein at least some of the transparent microspheres each comprise anisolated reflective layer that is present on a portion of the protrudingsurface area of the transparent microsphere.

Embodiment 35 is the intermediate article of embodiment 34 wherein atleast some of the transparent microspheres further comprise at least oneintervening layer, at least a portion of which is disposed between thetransparent microsphere and the isolated reflective layer.

Embodiment 36 is the intermediate article of any of embodiments 34-35wherein the isolated reflective layers of the intermediate article arenonuniform reflective layers configured so that the percent areacoverage of protruding surface areas of transparent microspheres by thelocally-laminated, isolated reflective layers exhibits a coefficient ofvariation greater than 0.05.

Embodiment 37 is the intermediate article of any of embodiments 34-35wherein the isolated reflective layers of the intermediate article arenonuniform reflective layers configured so that the percent areacoverage of protruding surface areas of transparent microspheres by thelocally-laminated, isolated reflective layers exhibits a coefficient ofvariation greater than 0.10.

Embodiment 38 is a method of making a retroreflective article comprisinga plurality of retroreflective elements at least some of which comprisean embedded reflective layer, the method comprising: disposingreflective layers or reflective layer precursors onto portions ofprotruding areas of at least some transparent microspheres that areborne by a carrier layer and that are partially embedded therein; then,if reflective layer precursors are present, transforming the reflectivelayer precursors into reflective layers; then, disposing a binderprecursor on the carrier layer and on the protruding areas of thetransparent microspheres; then, solidifying the binder precursor to forma retroreflective article comprising a binder layer and in which thereflective layers are embedded between the transparent microspheres andthe binder layer in such manner that at least some of the embeddedreflective layers are localized reflective layers and so that eachembedded reflective layer covers a portion of an embedded surface areaof the transparent microsphere that is less than the entirety of theembedded surface area of the transparent microsphere.

Embodiment 39 is the method of embodiment 38 wherein the disposing ofreflective layers or reflective layer precursors onto portions ofprotruding areas of at least some transparent microspheres that areborne by a carrier layer and that are partially embedded therein,comprises: printing reflective layer precursors onto the portions of theprotruding areas of some of the transparent microspheres; and, whereinthe transforming the reflective layer precursors into localizedreflective layers comprises solidifying the printed reflective layerprecursors to form localized reflective layers.

Embodiment 40 is the method of embodiment 38 wherein the disposing ofreflective layers or reflective layer precursors onto portions ofprotruding areas of at least some transparent microspheres that areborne by a carrier layer and that are partially embedded therein,comprises: disposing etchable reflective layers onto the protrudingareas of the transparent microspheres; then, disposing an etch-resistantmasking material onto portions of the etchable reflective layers thatare disposed on the protruding areas of the transparent microspheres;then, etching away portions of the etchable reflective layers that arenot masked by the etch-resistant masking material, to leave behindlocalized reflective layers.

Embodiment 41 is a retroreflective article of any of embodiments 1-29,made by the method of any of embodiments 38-40.

Embodiment 42 is a method of making an intermediate article comprising aplurality of transparent microspheres at least some of which comprise anisolated reflective layer, the method comprising: disposing reflectivelayers or reflective layer precursors onto portions of protruding areasof at least some transparent microspheres that are borne by a carrierlayer and that are partially embedded therein; and, if reflective layerprecursors are present, transforming the reflective layer precursorsinto reflective layers.

Examples

Materials Designation Description Resin 1 A co-polyester solution underthe trade designation VITEL ™ 3580 from Bostik Company (Wauwatosa, WI).Resin 2 A co-polyester solution under the trade designation VITEL ™VPE-5833 from Bostik Company (Wauwatosa, WI). SILANE-1 Agamma-isocyanatopropyltriethoxysilane under the trade name SILQUEST A-1310 OR A-LINK 25, available from Momentive Performance Materials Inc.,Albany, NY. ICN 1 A liquid aromatic polyisocyanide polymer based ontoluene diisocyanate, under the trade designation DESMODUR L-75 fromCovelco, Pittsburgh, PA. Pigment 1 A fluorescent lime-yellow pigmentpowder under the trade designation GT-17 SATURN YELLOW from Day GloColor Corporation, Cleveland, Ohio. CAT 1 A liquid catalyst based onDibutyltin dilaurate under the trade designation DABCO ™ T-12 fromEvonik GmbH, Essen, Germany. MEK Methyl ethyl ketone (reagent grade)MIBK Methyl isobutyl ketone (reagent grade) Ink-1 Silver ink under thetrade name PChem PFI-722 silver Ink from Novacentrix, Austin, TX. Ink-2A silver ink under the trade name TEC-PR-010 ink from Inktec, Inc.Gyeonggi- do, Korea Ink-3 Etch and plating resist ink under the tradename Nazdar 16935PC Etch & Plating Resist Black from Nazdar InkTechnologies, Shawnee, KS Xylene Dimethylbenzene (reagent grade)Etchant-1 A 50 mM/100 mM mixture of reagent grade ferric nitrate andthoiurea Ink-4 Red ink under the trade name Nazdar 9313 Base Warm RedBW5 from Nazdar Ink Technologies, Shawnee, KS. Acrylate-1 An acrylateliquid based on tricyclodecane dimethanol diacrylate, under the tradename of SARTOMER SR833S from Sartomer USA (Exton, PA) Heatseal Film -1An aluminized biaxially-oriented polypropylene film under the trade nameTorayFAN PMX2 commercially available from Toray Plastics (America), Inc.(North Kingstown, RI) Resin 3 A linear, triblock copolymer based onstyrene and isoprene with a polystyrene content of 19% under the tradename Kraton D1114 commercially available from Kraton Corporation(Houston, TX) Resin 4 A polyolefin plastomer resin under the trade nameAffinity 1850 from The Dow Chemical Company (Midland, MI) Silane 2 Abutylaminopropyltrimethoxy silane under the trade name Dynasylan 1189commercially available from Evonik Industries (Essen, Germany) Resin 5An acidic acrylate oligomer under the trade name of SARTOMER CN147 fromSartomer USA (Exton, PA) Pigment 2 A titanium dioxide based pigmentunder the trade name Dupont Ti-Pure R706 available from The ChemoursCompany (Wilmington, DE) Pigment 3 A black pigment under the trade nameOrasol Black X51, Florham Park, NJ

Test Methods

Retroreflectivity Measurement

Articles were evaluated for retroreflectivity performance by measuringthe coefficient of retroreflectivity using a RoadVista 933retroreflectometer (RoadVista, San Diego, Calif.).

The coefficient of retroreflectivity (R_(A)) is described in U.S. Pat.No. 3,700,305:

R_(A)=E₁*d²/E₂*A

R_(A)=retroreflective intensity

E₁=illumination incident upon the receiver

E₂=illumination incident upon a plane perpendicular to the incident rayof the specimen position, measured in the same units as E₁

d=distance from the specimen to the projector

A=area of the test surface

The retroreflectivity measurement test procedure followed the testcriteria described in ASTM E8 10-03 (2013)—Standard Test Method forCoefficient of Retroreflective Sheeting using the Coplanar Geometry.Retroreflective units are reported in cd/lux/m². High visibility safetyapparel standards such as ANSI/ISEA 107-2010 and ISO 20471:2013 requireminimum retroreflective coefficient performance at specific combinationsof entrance and observation angle. Entrance angle is defined as theangle between the illumination axis and the retroreflector axis. Theobservation angle is defined as the angle between the illumination axisand the observation axis. Unless otherwise stated, the entrance anglewas 5 degrees, and the observation angle was 0.2 degrees. In some cases,samples were evaluated in a “32-angle” test battery of the typedescribed in Table 5 of ISO 20471:2013 and often used in the evaluationof e.g. safety apparel. In such testing, the observation angle, theentrance angle, and the orientation of the sample (0 or 90 degrees) isvaried. It will be understood, however, that not all uses willnecessarily require a retroreflective article to meet this particularstandard.

Color Measurement

The color of a retroreflective article can be described in terms of aluminance-chromaticity color space (Yxy), where Y is the colorluminance, and x and y are chromaticity coordinates. These values arerelated to the CIE XYZ color space (International Commission onIllumination (CIE 1931)):x=X/(X+Y+Z)y=Y/(X+Y+Z)The advantage of using Yxy color space is that the chromaticity can beplotted on a chart, usually called the CIE x-y chromaticity diagram.This color representation/nomenclature is used in high visibility safetyapparel regulatory standards such as ANSI/ISEA 107-2010 and ISO20471:2013. The color measurement procedure is in accordance with theprocedure outlined in ASTM E 308-90, where the following operatingparameters are as set forth below:

Standard illuminant: D65 daylight illuminant

Standard observer: CIE (International Commissioner of Illumination) 19312°

Wavelength interval: 400-700 nanometers at 10 nanometer intervals

Incident light: 0° on sample plane

Viewing: 45° through a ring of 16 fiber optic receptor stations

Area of view: one inch

Port size: one inch

In certain examples, an alternate color representation (L*a*b*) is used.The definition of this color space is described as CIE L*a*b*1976 colorspace. Knowing these parameters, a person of ordinary skill canreproduce this test. For a further discussion of the operatingparameters see ASTM E 1164-93.

Peel Force

90 Degree Peel Method

Peel force was measured using a T-Peel test according to ASTM D1876-08.Samples measuring 2 inches by 6 inches (50×150 mm) were cut from sheetsof coated film and laid coated side up on a smooth clean surface. Apiece of Scotch® 3850 Shipping Packaging Tape (3M Corporation, St. Paul,Minn.) was cut measuring about 8 inches (200 mm) long, aligned with thelong edge of the sample, and applied to the coated side of the samplewith a hard rubber hand roller using firm pressure. Care was taken toavoid the formation of creases or any entrapped air. A 1 inch (25 mm)wide test strip was slit out of the center of the laminated sample, inthe long dimension, ensuring the two edge cuts were clean and parallel.The first one-quarter to one-half inch of the laminated test strip wasseparated and the two separated ends were secured in the grips of atensile tester which was configured to conduct testing in a T-Peelgeometry at a peel rate of 3 inches/minute (75 mm per minute) and recordthe peel force in grams. The peel was initiated and allowed to continueuntil at least 4 inches of the test strip length had been separated. Theseparated surfaces of the test strip were examined to determine locationof failure and the peel value was recorded in grams per linear inch.

180 Degree Peel Method

Same sample preparation as for the 90 degree peel method, except thetest was constructed in a 180 degree peel geometry with a 2 inch (50 nm)wide test strip.

Method for Making Temporary Bead Carrier Containing Glass Microspheres

In each of the Examples and Comparative Examples, glass microsphereswere partially and temporarily embedded in a carrier sheet. The carriersheet included paper juxtaposed against a polyethylene layer that wasabout 25 to 50 micrometers thick. The carrier sheet was heated in aconvection oven to 220° F. (104° C.), then the microspheres were pouredonto polyethylene side of the sheet and left for 60 seconds. The sheetwas removed from the oven and allowed to cool to room temperature.Excess beads were poured off the sheet, and the sheet was then placed inan oven at 320° F. (160° C.) for 60 seconds. The sheet was removed fromthe oven and allowed to cool. The microspheres were partially embeddedin the polyethylene layer such that more than 50 percent of themicrospheres protruded.

Working Example 2-1

Example 2-1, and Examples 2-2-1 and 2-2-2, describe the use offlexographic printing methods to produce retroreflective articlescomprising embedded reflective layers.

The temporary bead carrier as described previously was roll-to-rollflexographically printed with Ink-1, using a flat (i.e. un-patterned andcontinuous) Dupont Cyrel 67 mil DPR photopolymer flexo plate, a 1.8billion cubic microns per square inch (BCM/in²) volume anilox roll, anda line speed of 35 fpm (10.8 meters per minute). The plate-to-aniloxroll and plate-to-impression roll gaps were initially set to a positionsuch that a continuous pattern of silver ink was transferred from theanilox roll to the plate roll and finally to the temporary bead carrier.The ink transfer efficiency was controlled by adjusting theplate-to-anilox and plate-to-impression roll gaps.

The silver-printed bead carrier was then dried using an infrared unitfrom Xeric Web Systems (Neenah, Wis.) with nine medium wave lamps set to100% power at 50 fpm (15.2 meters per minute, power output at poweroutput at 108 joules/in² (167.4 kJ/m²) at 15.2 meters per minute),followed by two air impingement ovens, each with six drying bars (FlexAir, Green Bay, Wis.), with an air temperature of 275° F. (135° C.) andmanifold supply pressure of 15 psi (0.1 MPa). This produced the PrintedBead Carrier-1.

A solution consisting of 61 parts Resin 1, 11 parts Resin 2, 7 partsPigment 1, 2 parts ICN-1, 1 part SILANE-1, 1 part 10% CAT-1 in MEK, 11parts MEK and 7 parts MIBK was mixed into a MAX 40 Speedmixer cup, andfurther mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-K Speedmixer(FlackTek Inc, Landrum, S.C.). The solution was coated onto the PrintedBead Carrier-1, using a laboratory notch bar coater with a 0.008 inch(0.2 millimeter) gap. The coated sample was dried for 30 seconds at 160°F. (71.1° C.), then dried for an additional 3 minutes at 180° F. (82.2°C.). The dried coating thus formed a binder layer of the general typedescribed earlier herein. The sample was then laminated onto a polyamidefabric using a roll laminator at 220° F. (104.4° C.) at a roller speedof approximately 32 inches per minute (0.8 meter per minute). InventiveExample 2-1 was obtained by removal of the bead carrier sheet, withR_(A) (at EA/OA of 5/0.2) of 274, Y of 63.0, x of 0.3952, and y of0.5176.

Working Examples 2-2-1 and 2-2-2

The temporary bead carrier as described previously was roll-to-rollflexographically printed with Ink-2, using a flat (i.e. un-patterned andcontinuous) Dupont Cyrel 67 mil DPR photopolymer flexo plate, a 4.0BCM/in² volume anilox roll, and a line speed of 20 fpm (6.1 meters perminute). The plate-to-anilox roll and plate-to-impression roll gaps wereinitially set to a position such that a continuous pattern of silver inkwas transferred from the anilox roll to the plate roll and finally tothe temporary bead carrier. The ink transfer efficiency was controlledby adjusting the plate-to-anilox and plate-to-impression roll gaps.

The printed bead carrier was then dried using two infrared units fromXeric Web Systems (Neenah, Wis.), each with nine medium wave lamps setto 100% power at 20 fpm (6.1 meters per minute), power output at 135joules/in² (209.3 kJ/m²), followed by two air impingement ovens, eachwith six drying bars (Flex Air, Green Bay, Wis.), with an airtemperature of 275° F. (135° C.) and manifold supply pressure of 15 psi(0.1 MPa). This produced the Printed Bead Carrier-2.

A solution consisting of 61 parts Resin 1, 11 parts Resin 2, 7 partsPigment 1, 2 parts ICN-1, 1 part SILANE-1, 1 part 10% CAT-1 in MEK, 11parts MEK and 7 parts MIBK was mixed into a MAX 40 Speedmixer cup, andfurther mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-K Speedmixer(FlackTek Inc, Landrum, S.C.). The solution was coated onto the PrintedBead Carrier-2 using a laboratory notch bar coater with a 0.008 inch(0.2 millimeter) gap. The coated sample was dried for 30 seconds at 160°F. (71.1° C.), then dried for an additional 3 minutes at 180° F. (82.2°C.). The sample was then laminated onto a polyamide fabric using a rolllaminator at 220° F. (104.4° C.) at a roller speed of approximately 32inches per minute (0.8 meter per minute). Inventive Example 2-2-1 wasobtained by removal of the bead carrier sheet, with R_(A) of 249, Y of26.2, x of 0.3788, and y of 0.4772.

The Printed Bead Carrier-2 was further cut to approximately 6×8 inch(150×200 millimeters) coupons and flash lamp sintered with a XenonS-2100 16″ linear lamp system (Xenon Corporation, Wilmington Mass.).Flash lamp treated samples were exposed to successive pulses from thelinear xenon flash tube while being translated under the tube. Thesamples were translated in a direction orthogonal to the axis of thetube in synchronization with the timing of light pulses so as to treatthe entire area of each sample according to the following defined pulsedesign: speed of 9 mm/s, step of 18 mm, voltage of 3 kV, and pulseduration of 2.5 ms. The lamp was also defocused to create a widerexposure area by increasing the distance from the substrate by 1 inchfrom the optimal lamp height. This produced the Printed Bead Carrier-3.

A solution consisting of 61 parts Resin 1, 11 parts Resin 2, 7 partsPigment 1, 2 parts ICN-1, 1 part SILANE-1, 1 part 10% CAT-1 in MEK, 11parts MEK and 7 parts MIBK was mixed into a MAX 40 Speedmixer cup, andfurther mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-K Speedmixer(FlackTek Inc, Landrum, S.C.). The solution was coated onto the PrintedBead Carrier-3 using a laboratory notch bar coater with a 0.008 inch(0.2 millimeter) gap. The coated sample was dried for 30 seconds at 160°F. (71.1° C.), then dried for an additional 3 minutes at 180° F. (82.2°C.). The sample was then laminated onto a polyamide fabric using a rolllaminator at 220° F. (104.4° C.) at a roller speed of approximately 32inches per minute (0.8 meter per minute). Inventive Example 2-2-2 wasobtained by removal of the bead carrier sheet, and was tested and foundto exhibit R_(A) of 534, Y of 41.8, x of 0.3858, and y of 0.4861.

Working Example 2.3

Example 2.3 describes the use of local lamination methods to produceretroreflective articles comprising embedded reflective layers. ThisExample uses a conformal (elastomeric) substrate (referred to in theExample as an elastomeric transfer adhesive) to assist in the locallamination.

The following examples describe five general parts:

A. Making an article that has a multi-layer transferrable reflectorlayer

B. Making an elastomeric transfer adhesive

C. Transferring the reflector layer from (A) to (B)

D. Transferring the reflector layer from (C) to a bead carrier

E. Making a retroreflective article from (D)

Example 2.3.1

2.3.1.A (Part A)

Optical films were made on a vacuum coater similar to the coaterdescribed in U.S. Pat. No. 8,658,248 (Anderson et al.) and U.S. Pat. No.7,018,713 (Padiyath, et al.). This coater was threaded up with asubstrate in the form of an indefinite length roll of 980 microinch(0.0250 mm) thick, 14 inch (35.6 cm) wide Heatseal Film-1. Thissubstrate was then advanced at a constant line speed of 32 fpm (9.8m/min).

A first organic layer was formed on the substrate by applyingAcrylate-1, by ultrasonic atomization and flash evaporation to make acoating width of 12.5 inches (31.8 cm). This monomeric coating wassubsequently cured immediately downstream with an electron beam curinggun operating at 7.0 kV and 10.0 mA. The flow of liquid monomer into theevaporator was 0.67 ml/min, the nitrogen gas flow rate was 100 sccm andthe evaporator temperature was set at 500° F. (260° C.). The processdrum temperature was 14° F. (−10° C.).

On top of this first organic layer, a silver reflecting layer wasdeposited by DC sputtering of a >99% silver cathode target. The systemwas operated at 3 kW with a 30 fpm (9.1 meters per minute) line speed.Two subsequent depositions with the same power and line-speed were doneto create a 90 nm layer of silver.

On top of this silver layer, an oxide layer of silicon aluminum oxidewas deposited by AC reactive sputtering. The cathode had aSi(90%)/Al(10%) target obtained from Soleras Advanced Coatings US, ofBiddeford, (ME). The voltage for the cathode during sputtering wascontrolled by a feed-back control loop that monitored the voltage andcontrolled the oxygen flow such that the voltage would remain high andnot crash the target voltage. The system was operated at 16 kW of powerto deposit a 12 nm thick layer of silicon aluminum oxide onto the silverreflecting layer. (Silicon aluminum oxide may be referred to herein asSiAlO_(x) for convenience; this does not signify any particularstoichiometric ratio of any of the components.)

The aluminum surface of the Heatseal Film-1 film and the first organiclayer would decouple with a 180 Peel force of 7.2 On (0.283 g per mm).

2.3.1.E (Part B) Making an Elastomeric Transfer Adhesive

Elastomeric transfer adhesive films containing one or more layers weremade using cast co-extrusion processes as described in co-extrusionpatents such as U.S. Pat. Nos. 5,223,276, 9,327,441 and WO9936248, thedisclosures of which are incorporated herein by reference thereto.

3-layer transfer films: A 3-layer feed block (ABA plug) in combinationwith a single layer manifold die (10-inch (254 mm) width) was used togenerate 3-layer films with an elastomeric core and polyolefin plastomerskin. The elastomeric core was made using Resin 3 and the polymerplastomer skin using Resin 4. The core material was melted at 400° F.(204° C.) in a single screw extruder and fed into one of the inlets ofthe 3-layer feed block, while the skin material was melted at 360° F.(182° C.) in a twin-screw extruder and fed into a second inlet in thefeed block where it split into two streams to encapsulate the core layeron both sides. The composite film was then cast directly from the dieonto a chilled roll maintained at 60-70° F. (15-21° C.). The caliper andcore-skin ratio was varied by adjusting the line speed of the winderunit and changing the configuration of the floating vanes in the feedblock respectively. Multilayer films with thickness ranging from0.002-0.005 inches (0.051-0.127 mm) and core-skin ratio ranging from10-30 were produced and used for the transfer process.

2.3.1.0 (Part C)

The three-layer elastomer adhesive was laminated to the articledescribed in Part A using an Akiles ProLam Plus 330 13″ Pouch Laminator(Mira Loma,) with a setpoint of 171° F. (77° C.) with the SiAlO_(x)surface in contact with the elastomer transfer adhesive surface. TheHeatseal Film 1 was removed from the construction and discarded. The 180Peel test showed that the multilayer film of acrylate/Ag/SiAlO_(x) couldbe removed from the surface of the planar elastomer with peel forces of25 On (0.98 g/mm).

2.3.1.D (Part D)

A solution containing 6.18 parts Resin1, 0.13 parts SILANE-1, 0.5 partsICN 1, and 33.41 parts MEK was mixed into a MAX 40 Speedmixer cup, andfurther mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-K Speedmixer(FlackTek Inc, Landrum, S.C.). The solution was coated onto thetemporary bead carrier using a notch-bar coater gapped at 51micrometers. The sample was dried for 3 minutes at 150° F. (65.5° C.)with an additional curing for 4 minutes at 200° F. (93.3° C.). Thisproduced the Polymer Coated Bead Carrier.

The elastomeric transfer adhesive with the weakly boundacrylate/Ag/SiAlO_(x) multilayer optical reflector film was pressedagainst the Polymer Coated Bead Carrier at 180° F. (82° C.) with alamination force of 40 lb/in (714 g/mm) of lamination force. In thisstep, the acylate surface makes contact with the polymer surface of thepolymer coated bead carrier. Then the elastomeric transfer adhesive waspulled away from the Polymer Coated Bead Carrier to produce theTransferred Bead Carrier-1.

2.3.1.E (Part E)

A solution consisting of 61 parts Resin 1, 11 parts Resin 2, 7 partsPigment 1, 2 parts ICN-1, 1 part SILANE-1, 1 part 10% CAT-1 in MEK, 11parts MEK and 7 parts MIBK was mixed into a MAX 40 Speedmixer cup, andfurther mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-K Speedmixer(FlackTek Inc, Landrum, S.C.). The solution was coated onto theTransferred Bead Carrier-1 using a laboratory notch bar coater with a0.008 inch (0.2 millimeter) gap. The coated sample was dried for 30seconds at 160° F. (71.1° C.), then dried for an additional 3 minutes at180° F. (82.2° C.). The sample was then laminated onto a polyamidefabric using a roll laminator at 220° F. (104.4° C.) at a roller speedof approximately 32 inches per minute (0.8 meter per minute). InventiveExample 2-3-1 was obtained by removal of the bead carrier sheet, and wastested and found to exhibit R_(A) of 616, Y of 52.9, x of 0.3642, and yof 0.4795. Table 2.3.1 presents the results of a “32-angle” test.Although not noted explicitly in the Table, each pair of observations(at identical observation angles and identical entrance angles) are fororientation angles of 0 and 90 degrees. The obtained results (therightmost column of Table 2.3.1) are compared to the ANSI minimumspecification.

TABLE 2.3.1 ANSI/ISE Observation Entrance A 107 Angle Angle MinimumR_(A) (degrees) (degrees) Spec. (cd/lx-m²) 0.2 5 330 609 0.2 5 330 6160.2 20 290 467 0.2 20 290 525 0.2 30 180 349 0.2 30 180 408 0.2 40 65264 0.2 40 65 324 0.33 5 250 373 0.33 5 250 379 0.33 20 200 292 0.33 20200 327 0.33 30 170 228 0.33 30 170 258 0.33 40 60 190 0.33 40 60 217 15 25 52.1 1 5 25 51.7 1 20 15 39.9 1 20 15 45.2 1 30 12 31.5 1 30 1236.9 1 40 10 23 1 40 10 28 1.5 5 10 15.9 1.5 5 10 16.4 1.5 20 7 13.7 1.520 7 14.9 1.5 30 5 11.4 1.5 30 5 12.8 1.5 40 4 10.7 1.5 40 4 10.2

Example 2.3.2

As in Example 2-3-1, except:

In 2.3.2.B (Part B) a single layer elastomeric transfer adhesive wasmade in a 6-inch single manifold die using Resin 3. The raw material wasmelted in a single screw extruder at 400° F. (204° C.) and cast onto achilled roll maintained at room temperature. Films with thicknessesranging from 0.001-0.004 inches (0.025-0.1 mm) were produced byadjusting the line speed of the winder unit and used for the mirrortransfer process. This material allowed the lamination of 2.3.2.0 and2.3.2.D (Part C and D) to be done at 77° F. (25° C.) without additionalheating. In 2.3.2.D (Part D) if less than 40 lb/in (714 g/mm) laminationforce was used, less than full-transfer, or partial transfer, of themirror was facilitated. This led to lower retroreflectivity(R_(A)=ranging from 20 to 400 cdlx-m²) with the value dependent on thepressure used. Then the elastomeric transfer adhesive was pulled awayfrom the Polymer Coated Bead Carrier to produce the Transferred BeadCarrier-2.

Example 2.3.3

2.3.3.A (Part A)

A transfer multilayer optical reflector was prepared as follows:

A transfer reflector film is described and was made on a roll to rollvacuum coater similar to the coater described in U.S. Patent ApplicationNo. 20100316852 (Condo, et al.) with the addition of a second evaporatorand curing system located between the plasma pretreatment station andthe first sputtering system, and using evaporators as described in U.S.Pat. No. 8,658,248 (Anderson and Ramos).

This coater was outfitted with a substrate in the form of a 1000 ft (305m) length roll of 0.002 in (0.05 mm) thick, 14 inch (35.6 cm) widepolyethylene terephthalate (PET) film manufactured by 3M Company. Thesubstrate was prepared for coating by subjecting it to a nitrogen plasmatreatment to improve the adhesion of the metallic layer. The film wastreated with a nitrogen plasma operating at 120 W using a titaniumcathode, using a web speed of 32 fpm (9.8 meters/min) and maintainingthe backside of the film in contact with a coating drum chilled to 14°F. (−10° C.).

On this prepared PET substrate, the release layer of SiAl was depositedin-line with the previous plasma treatment step. The cathode had aSi(90%)/Al(10%) target obtained from Soleras Advanced Coatings US, ofBiddeford, (ME). A conventional AC sputtering process employing Ar gasand operated at 24 kW of power was used to deposit a 37 nm thick layerof SiAl alloy onto the substrate. The SiAl coated PET substrate was thenrewound.

On this SiAl release layer, a layer of Acrylate-1 was deposited in-lineon top of the SiAl layer. The acrylate layer was applied by ultrasonicatomization and flash evaporation to make a coating width of 12.5 inches(31.8 cm). The flow rate of this mixture into the atomizer was 0.33ml/min to achieve a 94 nm layer, the gas flow rate was 60 standard cubiccentimeters per minute (sccm), and the evaporator temperature was 500°F. (260° C.). Once condensed onto the SiAl layer, this monomeric coatingwas cured immediately with an electron beam curing gun operating at 7.0kV and 10.0 mA.

On this acrylate layer, an inorganic oxide layer of niobium oxide wasapplied in a separate pass. The cathode ceramic or suboxide NbOx targetobtained from Soleras Advanced Coatings US, of Biddeford, (ME) was used.More specifically, a conventional DC sputtering process operated at 2 kWof power was employed to deposit an approximately 66 nm thick layer ofNbOx onto the substrate to form a quarter wave optical thickness at aline speed of 1 fpm (0.3 m/min) using a 450 sccm Ar and 14 sccm O2 gasflow.

On this niobium oxide layer, an acrylate layer was formed. Thispolymeric layer was produced by atomization and evaporation of a monomermixture containing 94 parts Acrylate-1, 3 parts Silane-2), and 3 partsResin-5 in a separate pass on top of the niobium oxide layer. Theacrylate layer was applied by ultrasonic atomization and flashevaporation to make a coating width of 12.5 inches (31.8 cm). The flowrate of this mixture into the atomizer was 0.66 ml/min to achieve a 188nm layer at 32 fpm (9.8 meters per minute), the gas flow rate was 60standard cubic centimeters per minute (sccm), and the evaporatortemperature was 500° F. (260° C.). Once condensed onto the niobium oxidelayer, this monomeric coating was cured immediately with an electronbeam curing gun operating at 7.0 kV and 10.0 mA.

2.3.3.0 (Part C)

The three-layer elastomer described in 2.3.1.B was laminated to thearticle described in 2.3.3.A (Part A) at 171° F. (77° C.) and then theSiAl coated PET was removed and discarded.

2.3.3.D (Part D)

The elastomeric transfer adhesive with the weakly boundacrylate/NbOx/Acrylate multilayer optical reflector film was pressedagainst the Polymer Coated Bead Carrier at 180° F. (82° C.) with alamination force of 50 lb/in (893 g/mm). In this step, the acylatesurface makes contact with the polymer surface of the polymer coatedbead carrier. Then the elastomeric transfer adhesive was pulled awayfrom the Polymer Coated Bead Carrier to produce the Transferred BeadCarrier-3.

2.3.3.E (Part E)

A solution consisting of 61 parts Resin 1, 11 parts Resin 2, 7 partsPigment 1, 2 parts ICN-1, 1 part SILANE-1, 1 part 10% CAT-1 in MEK, 11parts MEK and 7 parts MIBK was mixed into a MAX 40 Speedmixer cup, andfurther mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-K Speedmixer(FlackTek Inc, Landrum, S.C.). The solution was coated onto theTransferred Bead Carrier-3 using a laboratory notch bar coater with a0.008 inch (0.2 millimeter) gap. The coated sample was dried for 30seconds at 160° F. (71.1° C.), then dried for an additional 3 minutes at180° F. (82.2° C.). The sample was then laminated onto a polyamidefabric using a roll laminator at 220° F. (104.4° C.) at a roller speedof approximately 32 inches per minute (0.8 meter per minute). InventiveExample 2-3-3 was obtained by removal of the bead carrier sheet. Thearticle has an R_(A) of 105, Y of 110, x of 0.3569, and y of 0.4805. Itwill be appreciated that this article comprised a reflecting layer inthe guise of a dielectric stack rather than a reflecting metal layer.

Working Example 2.4

Example 2.4 describes the use of local lamination methods to produceretroreflective articles comprising embedded reflective layers. ThisExample uses direct transfer (without the assistance of a conformal(elastomeric) substrate) lamination methods.

The following direct transfer examples describe three general parts:

A. Making an article that has a multi-layer transferrable reflectorlayer

B. Transferring the reflector layer from (A) directly to a bead coat

C. Making a retroreflective article from (B)

Example 2.4.1

2.4.1 part A

A transfer mirror film is described in this Example and was made on aroll to roll vacuum coater similar to the coater described in U.S.Patent Application No. 20100316852 with the addition of a secondevaporator and curing system located between the plasma pretreatmentstation and the first sputtering system, and using evaporators asdescribed in U.S. Pat. No. 8,658,248.

This coater was threaded up with a substrate in the form of anindefinite length roll of 0.001 inch (0.0250 mm) thick, 14 inch (356 mm)wide Heatseal Film-1. The metal side of the film was coated using a webspeed of 9.8 meters/min and maintaining the backside of the film incontact with a coating drum chilled to −10° C. A layer of Acrylate-1 wasdeposited in-line on top of the aluminum metalized side of the HeatsealFilm-1. The acrylate layer was applied by ultrasonic atomization andflash evaporation to make a coating width of 12.5 inches (31.8 cm). Theflow rate of this mixture into the atomizer was 0.67 ml/min to achieve a188 nm layer, the gas flow rate was 60 standard cubic centimeters perminute (sccm), and the evaporator temperature was 260° C. Once condensedonto the Al layer, this monomeric coating was cured immediately with anelectron beam curing gun operating at 7.0 kV and 10.0 mA.

On this acrylate layer, a reflecting layer of Ag was applied using acathode Ag target (ACI Alloys of San Jose, Calif.). This Ag metal layerwas deposited by a conventional DC sputtering process employing Ar gas,operated at 3 kW of power, and at a 9.8 meters/min line speed to perpass for 3 passes to deposit a 60 nm thick layer of Ag.

On this Ag reflecting layer, an inorganic oxide layer was applied. Thisoxide material was laid down by an AC reactive sputter depositionprocess employing a 40 kHz AC power supply. The cathode had aSi(90%)/Al(10%) rotary target obtained from Soleras Advanced CoatingsUS, of Biddeford, (ME). The voltage for the cathode during sputteringwas controlled by a feed-back control loop that monitored the voltageand controlled the oxygen flow such that the voltage would remain highand not crash the target voltage. The system was operated at 16 kW ofpower and 32 fpm to deposit a 12 nm thick layer of silicon aluminumoxide onto the Ag layer.

2.4.1 Part B

The Heatseal Film-1 substrate with the weakly boundacrylate/Ag/SiAlO_(x) multilayer optical reflector film was pressedagainst the Polymer Coated Bead Carrier at room temperature with 500lb/linear inch (87.5 kN/m) of lamination force at 10 fpm (4.2 mm persecond). The SiAlO_(x) surface was in contact with the polymer coatedside of the carrier. A silicone rubber sleeve with a 78D hardness backedthe Heatseal Film-1 substrate and a steel roll backed the paper side ofthe Polymer Coated Bead Carrier. After lamination, the Heatseal Film −1film was removed to produce the Transferred Bead Carrier-4.

2.4.1 Part C

A mixture consisting of 61 parts Resin 1, 11 parts Resin 2, 7 partsPigment 1, 2 parts ICN-1, 1 part SILANE-1, 1 part 10% CAT-1 in MEK, 11parts MEK and 7 parts MIBK was mixed into a MAX 40 Speedmixer cup, andfurther mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-K Speedmixer(FlackTek Inc, Landrum, S.C.). The solution was coated onto theTransferred Bead Carrier-4 using a laboratory notch bar coater with a0.008 inch (0.2 millimeter) gap. The coated sample was dried for 30seconds at 160° F. (71.1° C.), then dried for an additional 3 minutes at180° F. (82.2° C.). The sample was then laminated onto a polyamidefabric using a roll laminator at 220° F. (104.4° C.) at a roller speedof approximately 32 inches per minute (0.8 meter per minute). InventiveExample 2-4-1 was obtained by removal of the bead carrier sheet, withR_(A) of 386, Y of 98, x of 0.3531, and y of 0.4810.

Example 2.4.2

A solution consisting of 84 parts Resin 1, 8 parts Pigment 2, 4 partsICN-1, 1 part SILANE-1, 1 part 10% CAT-1 in MEK was mixed into a MAX 40Speedmixer cup, and further mixed at 2400 rpm for 60 seconds in a DAC150.1 FVZ-K Speedmixer (FlackTek Inc, Landrum, S.C.). The solution wascoated onto the Transferred Bead Carrier-4 using a laboratory notch barcoater with a 0.008 inch (0.2 mm) gap. The coated sample was dried for30 seconds at 190° F. (87.8° C.), laminated to a polyester white fabricusing a hand roller, then dried for an additional 6 minutes at 215° F.(101.7° C.). Inventive Example 2-4-2 was obtained by removal of the beadcarrier sheet, and exhibited R_(A) of 394, L* of 81.2, a* of −0.9, b* of1.1.

Example 2.4.3

A solution consisting of 84 parts Resin 1, 4 parts Pigment 3, 4 partsICN-1, 1 part SILANE-1, 1 part 10% CAT-1 in MEK was mixed into a MAX 40Speedmixer cup, and further mixed at 2400 rpm for 60 seconds in a DAC150.1 FVZ-K Speedmixer (FlackTek Inc, Landrum, S.C.). The solution wascoated onto the Transferred Bead Carrier-4 using a laboratory notch barcoater with a 0.008 inch (0.2 mm) gap. The coated sample was dried for30 seconds at 190° F. (87.8° C.), laminated to a polyester white fabricusing a hand roller, then dried for an additional 6 minutes at 215° F.(101.7° C.). Inventive Example 2-4-3 was obtained by removal of the beadcarrier sheet, with R_(A) of 277, L* of 25.3, a* of 0.7, b* of −1.3.

Example 2.4.4

A solution consisting of 84 parts Resin 1, 4 parts ICN-1, 1 partSILANE-1, 1 part 10% CAT-1 in MEK was mixed into a MAX 40 Speedmixercup, and further mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-KSpeedmixer (FlackTek Inc, Landrum, S.C.). The solution was coated ontothe Transferred Bead Carrier-4 using a laboratory notch bar coater witha 0.008 inch (0.2 mm) gap. The coated sample was dried for 30 seconds at190° F. (87.8° C.), and an additional 6 minutes at 215° F. (101.7° C.).The coating side of the sample was marked with a colorful graphic imageusing a permanent ink marker, and then laminated to a white cottonfabric using a hot melt adhesive. Inventive Example 2-4-4 was obtainedby removal of the bead carrier sheet, and exhibited R_(A) of 385. Thecolorful graphic image was clearly visible on the marked region ofExample 2-4-4. Example 2-4-4 had L* of 74.5, a* of 1.0, b* of −5.9 onthe unmarked region.

Example 2.4.5

2.4.5 Part A

A transfer mirror film is described in this Example and was made on aroll to roll vacuum coater similar to the coater described in U.S.Patent Application No. 20100316852 (Condo, et al.) with the addition ofa second evaporator and curing system located between the plasmapretreatment station and the first sputtering system, and usingevaporators as described in U.S. Pat. No. 8,658,248 (Anderson andRamos).

This coater was threaded up with a substrate in the form of anindefinite length roll of 0.001 inch (0.0250 mm) thick, 14 inch (35.6cm) wide Heatseal Film-1. The metal side of the film was coated using aweb speed of 9.8 meters/min and maintaining the backside of the film incontact with a coating drum chilled to 14° F. (−10° C.).

Acrylate-1 was then deposited on top of the aluminum coating of HeatsealFilm-1. The acrylate layer was applied using ultrasonic atomization andflash evaporation to make a coating width of 12.5 inches (31.8 cm). Theflow rate of this mixture into the atomizer was 0.67 ml/min to achieve a188 nm layer, the gas flow rate was 60 standard cubic centimeters perminute (sccm), and the evaporator temperature was 260° C. Once condensedonto the Al layer, this monomeric coating was cured immediately with anelectron beam curing gun operating at 7.0 kV and 10.0 mA.

On this acrylate layer, a reflecting layer of Ag was applied using acathode Ag target that was obtained from ACI Alloys of San Jose, Calif.This Ag metal layer was deposited by a conventional DC sputteringprocess employing Ar gas, operated at 3 kW of power, and at a 9.8meters/min line speed to per pass for 3 passes deposit a 60 nm thicklayer of Ag. This layer showed signs of corrosion if exposed to normallaboratory ambient conditions after one week.

2.4.5 Part B/C

Parts B and C for Inventive Example 2.4.5 used procedures previouslydescribed for Inventive Example 2.4.1, except for Part B, the transferwas conducted using a line speed of 3 fpm (0.91 m per minute). InventiveExample 2-4-5 had R_(A) of 368, Y of 101, x of 0.3916 and a y of 0.5389.

Working Example 3.1.1

Example 3.1.1 describes the use of resist/etch methods to produceretroreflective articles comprising embedded reflective layers.

A temporary bead carrier similar to that described previously wasconstructed using a PET backing sheet instead of paper.

A solution containing 6.18 parts Resin1, 0.13 parts SILANE-1, 0.5 partsICN 1, and 33.41 parts MEK was mixed into a MAX 40 Speedmixer cup, andfurther mixed at 2400 rpm for 60 seconds in a DAC 150.1 FVZ-K Speedmixer(FlackTek Inc, Landrum, S.C.). The solution was coated onto thetemporary bead carrier using a notch-bar coater gapped at 51micrometers. The sample was dried for 3 minutes at 150° F. (65.5° C.)with an additional curing for 4 minutes at 200° F. (93.3° C.). Thepolymer coated bead carrier was then coated with approximately 100nanometers of silver metal thin film using a thermal evaporation processin a vacuum coater operating at a vacuum of approximately 0.01 mTorr(1.3 mPa).

The metallized bead carrier was then roll-to-roll flexographicallyprinted with an ink comprising of 72 parts of Ink-3 and 28 parts Xylene,using a flat (i.e. un-patterned and continuous) sleeve with 38 Shore Ahardness, a 2.5 BCM/in² volume anilox roll and. The printed sheet wasthen dried at 135° C. oven for 5 seconds, then spray etched continuouslyusing a roll-to-roll etch line consisting of two festoons, each with twospray bars. An etching solution (Etchant-1) was prepared andcontinuously sprayed through BEX GS5 nozzles (BEX Inc. Ann Arbor,Mich.). Each spray bar had either 5 (first two bars) or three (last twobars) nozzles and was supplied by a 3 GPM, 45 psi diaphragm pump.Printed samples were etched at a web speed of 2 fpm, which gave a 150 sresidence time in the etchant. Samples remained wet for an additional 90seconds as they traveled to two dipped, deionized water rinses, beforefinally being dried using air knives.

After drying, an adhesive consisting of 61 parts Resin 1, 11 parts Resin2, 7 parts Pigment 1, 2 parts ICN-1, 1 part SILANE-1, 1 part 10% CAT-1in MEK, 11 parts MEK and 7 parts MIBK was coated onto the metalreflective layer using a laboratory notch bar coater with a 0.008 inch(0.2 mm) gap. The coated sample was dried for 30 seconds at 160° F.(71.1° C.), then dried for an additional 3 minutes at 180° F. (82.2°C.). The sample was then laminated onto a polyamide fabric using a rolllaminator at 220° F. (104.4° C.) at a roller speed of approximately 32inches per minute (813 mm/min).

After drying, the temporary bead carrier was removed to expose thebeaded surface of the sample 3.1-1, and both color and retroreflectivitycoefficient were measured. The sample exhibited R_(A) of 497, Y of 56.8,x of 0.3767 and a y of 0.5172.

Working Example 3.1-2

Example 3.1-2 describes the use of resist/etch methods to produceretroreflective articles comprising embedded reflective layers.

A temporary bead carrier as described previously was coated with anapproximately 200 nanometer thick layer of silver metal using a thermalevaporator operating at approximately 13 mPa. The resulting article wasflexographically printed with Ink-4 using a flat (i.e. un-patterned andcontinuous) Dupont Cyrel 67 mil DPR photopolymer flexo plate, using a1.8 BCM/sq inch volume anilox roll and cured by UV light. The printedsheet was then batch spray etched in a test box (Promax QPHA-3 spraynozzles from Spraying Systems Co., Hudson, N.H.) at 20 psi (1.38 MPa).An etching solution (Etchant 1) was used with an etch time of 50seconds. Samples were rinsed immediately after etching by dipping indeionized water and were subsequently dried under room ambientconditions.

After drying, an adhesive consisting of 61 parts Resin 1, 11 parts Resin2, 7 parts Pigment 1, 2 parts ICN-1, 1 part SILANE-1, 1 part 10% CAT-1in MEK, 11 parts MEK and 7 parts MIBK was coated onto the metalreflective layer using a laboratory notch bar coater with a 0.008 inch(0.2 mm) gap. The coated sample was dried for 30 seconds at 160° F.(71.1° C.), then dried for an additional 3 minutes at 180° F. (82.2°C.). The sample was then laminated onto a polyamide fabric using a rolllaminator at 220° F. (104.4° C.) at a roller speed of approximately 32inches per minute (813 mm/min).

The temporary carrier backing was then removed to expose the beadedsurface of the Inventive Example 3.1-2, and both color andretroreflectivity coefficient were measured. Retroreflectivitymeasurements were taken at combinations of entrance and observationangles described in ANSI/ISEA 107-2015. Measurements are shown in Table3.1-2. Table 3.1-2 also shows minimum retroreflectivity coefficientrequirement for a Class 2 or Class 3 high-visibility safety garment. ForComparative Example 3.1-1, no etching step was performed.

TABLE 3.1.2 Comparative Inventive Observation Entrance Minimum Example 1Example 2 0.2 5 330 665 525 0.2 5 330 668 511 0.2 20 290 683 521 0.2 20290 724 543 0.2 30 180 413 291 0.2 30 180 559 408 0.2 40 65 189 93 0.240 65 298 163 0.333 5 250 416 327 0.333 5 250 417 320 0.333 20 200 420325 0.333 20 200 428 327 0.333 30 170 320 226 0.333 30 170 388 276 0.33340 60 166 82.5 0.333 40 60 241 131 1 5 25 49.5 42 1 5 25 49.3 40 1 20 1552.5 43.7 1 20 15 52.5 43.3 1 30 12 61.1 39.4 1 30 12 75 48.8 1 40 1045.7 24.9 1 40 10 55.5 28.6 1.5 5 10 18.7 15.3 1.5 5 10 18.2 14.9 1.5 207 18.4 14.2 1.5 20 7 18.3 14.9 1.5 30 5 29.2 20.5 1.5 30 5 25.7 16.3 1.540 4 26.6 12 1.5 40 4 25.4 13.3

The foregoing Examples have been provided for clarity of understandingonly, and no unnecessary limitations are to be understood therefrom. Thetests and test results described in the Examples are intended to beillustrative rather than predictive, and variations in the testingprocedure can be expected to yield different results. All quantitativevalues in the Examples are understood to be approximate in view of thecommonly known tolerances involved in the procedures used.

It will be apparent to those skilled in the art that the specificexemplary elements, structures, features, details, configurations, etc.,that are disclosed herein can be modified and/or combined in numerousembodiments. All such variations and combinations are contemplated bythe inventor as being within the bounds of the conceived invention, notmerely those representative designs that were chosen to serve asexemplary illustrations. Thus, the scope of the present invention shouldnot be limited to the specific illustrative structures described herein,but rather extends at least to the structures described by the languageof the claims, and the equivalents of those structures. Any of theelements that are positively recited in this specification asalternatives may be explicitly included in the claims or excluded fromthe claims, in any combination as desired. Any of the elements orcombinations of elements that are recited in this specification inopen-ended language (e.g., comprise and derivatives thereof), areconsidered to additionally be recited in closed-ended language (e.g.,consist and derivatives thereof) and in partially closed-ended language(e.g., consist essentially, and derivatives thereof). Although varioustheories and possible mechanisms may have been discussed herein, in noevent should such discussions serve to limit the claimable subjectmatter. To the extent that there is any conflict or discrepancy betweenthis specification as written and the disclosure in any document that isincorporated by reference herein, this specification as written willcontrol.

What is claimed is:
 1. A retroreflective article comprising: a binderlayer; and, a plurality of retroreflective elements spaced over a lengthand breadth of a front side of the binder layer, each retroreflectiveelement comprising a transparent microsphere partially embedded in thebinder layer so as to exhibit an embedded surface area of thetransparent microsphere; wherein the article is configured so that atleast some of the retroreflective elements each comprise a reflectivelayer that is embedded between the transparent microsphere and thebinder layer and wherein at least some of the embedded reflective layersof the retroreflective article are localized reflective layers; whereineach localized, embedded reflective layer covers a portion of theembedded surface area of the transparent microsphere that is less thanthe entirety of the embedded surface area of the transparentmicrosphere, wherein the localized, embedded reflective layers areirregular and non-circular in shape and are positioned on thetransparent microspheres so that, on average, geometric centers of thelocalized, embedded reflective layers at least generally coincide withforward-rearward centerlines of the transparent microspheres and so thatthe localized, embedded reflective layers occupy angular arcs of, onaverage, from at least 15 degrees to less than 60 degrees; and, whereinall of the reflective layers of the retroreflective elements of theretroreflective article are metal reflective layers, with the provisothat none of the reflective layers of the retroreflective elements ofthe retroreflective article are, or include, a dielectric reflectinglayer, and with the further proviso that for each retroreflectiveelement in which the localized, embedded, metal reflective layer coversthe portion of the embedded surface area of the transparent microspherethat is less than the entirety of the embedded surface area of thetransparent microsphere, a remaining portion of the embedded surfacearea of the transparent microsphere that is not covered by thelocalized, embedded, metal reflective layer, does not comprise anyreflective material of any kind between the embedded surface area of thetransparent microsphere and the binder.
 2. The retroreflective articleof claim 1 wherein the article is configured so that at least 60% of theembedded reflective layers of the retroreflective article are localizedreflective layers.
 3. The retroreflective article of claim 1 wherein thearticle is configured so that at least some of the localized, embeddedreflective layers each cover a portion of the embedded surface area ofthe transparent microsphere that is at most 25% of the embedded surfacearea of the transparent microsphere.
 4. The retroreflective article ofclaim 1 wherein the article is configured so that at least some of thelocalized, embedded reflective layers each cover a portion of theembedded surface area of the transparent microsphere in such manner thatthe covered portion of the embedded surface area of the transparentmicrosphere is less than 15% of a total surface area of the transparentmicrosphere.
 5. The retroreflective article of claim 1 wherein thelocalized, embedded reflective layers each occupy an angular arc of atmost 180 degrees.
 6. The retroreflective article of claim 1 wherein atleast some of the localized, embedded reflective layers occupy anangular arc of, on average, from at least 15 degrees to at most 50degrees.
 7. The retroreflective article of claim 1 wherein the articleis configured to comprise at least some transparent microspheres that donot comprise reflective layers disposed thereon, and wherein thetransparent microspheres that comprise embedded reflective layers makeup from at least 5 percent to at most 95 percent of the total number oftransparent microspheres of the retroreflective article.
 8. Theretroreflective article of claim 1 wherein at least some of theretroreflective elements comprise an intervening layer at least aportion of which is disposed between the transparent microsphere and thebinder layer so that a localized, embedded reflective layer ispositioned between the intervening layer and the binder layer.
 9. Theretroreflective article of claim 1 wherein the binder layer comprises acolorant.
 10. The retroreflective article of claim 1 wherein at leastsome of the retroreflective elements comprise a localized layer that isan embedded layer that is embedded between the transparent microsphereand the localized, embedded reflective layer.
 11. The retroreflectivearticle of claim 1 wherein the article exhibits an initial coefficientof retroreflectivity (R_(A), measured at 0.2 degrees observation angleand 5 degrees entrance angle), in the absence of being exposed to a washcycle, of at least 100 candela per lux per square meter.
 12. Theretroreflective article of claim 1 wherein the article exhibits acoefficient of retroreflectivity (R_(A), measured at 0.2 degreesobservation angle and 5 degrees entrance angle) after 25 wash cycles,that is at least 30% of an initial coefficient of retroreflectivity inthe absence of being exposed to a wash cycle.
 13. A transfer articlecomprising the retroreflective article of claim 1 and a disposablecarrier layer on which the retroreflective article is detachablydisposed with at least some of the transparent microspheres in contactwith the carrier layer.
 14. An assembly comprising the retroreflectivearticle of claim 1 and a substrate, wherein the binder layer of theretroreflective article is coupled to the substrate with at least someof the retroreflective elements of the retroreflective article facingaway from the substrate.
 15. The substrate of claim 14 wherein thesubstrate is a fabric of a garment.
 16. The substrate of claim 14wherein the substrate is a support layer that is not a fabric of agarment.
 17. The retroreflective article of claim 1 wherein at least 50%of the retroreflective elements each comprise a reflective layer that isembedded between the transparent microsphere and the binder layer. 18.The retroreflective article of claim 1 wherein the microspheres arepartially embedded in the binder layer so that, on average, from 50 to80% of the diameters of the microspheres are embedded within the binderlayer.
 19. The retroreflective article of claim 1 wherein the binderlayer comprises nacreous reflective particles at a loading of from atleast 0.5 weight percent to at most 6 weight percent, on a dry-solidsbasis.
 20. The retroreflective article of claim 1 wherein the binderlayer comprises one or more fluorescent pigments.